Particulate Sorption Medium Prepared From Partially Decomposed Organic Matter

ABSTRACT

A process for the preparation from a partially decomposed organic material like peat a granulated or pelletized sorption medium using low-temperature, thermal activation of the sorption medium to produce a high degree of granule or pellet hardness balanced against an efficacious level of ion-exchange and adsorption capacity, followed by chemical treatment of the thermally-activated sorption material via an acid solution and a salt solution to increase its ion-exchange and adsorption performance while minimizing the transfer of natural impurities found in the sorption medium to an aqueous solution is provided by this invention. The sorption medium of this invention can be used in a variety of aqueous solution treatment processes, such as wastewater treatment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 13/841,526filed on Mar. 15, 2013 entitled “Particulate Sorption Medium Preparedfrom Partially Decomposed Organic Matter,” which is hereby incorporatedby reference.

FIELD OF THE INVENTION

This invention relates generally to particulate sorption media preparedfrom partially decomposed organic matter like peat, and morespecifically to granules made from such material that are thermallyactivated and chemically modified to provide them the requisite hardnessand sorption capacity for removing undesirable impurities from aqueoussolutions without introducing chemical contaminants naturally found inthe organic material into the aqueous solution.

BACKGROUND OF THE INVENTION

Many industrial manufacturers also face the problem of wastewaterscontaining heavy metals like arsenic, lead, mercury, cadmium, iron, andaluminum that are produced by their manufacturing process. Circuit boardmanufacturers, metal finishers, automotive, aerospace, and semiconductormanufacturing, electroplated metal parts/washing, textile dyes, andsteel are prime contributors. If dissolved in heavy-enoughconcentrations in the wastewater stream, they become toxic when they arenot metabolized by the body, and accumulate instead in the soft tissues.Heavy metal toxicity can result in damaged or reduced mental and centralnervous function, learning disabilities, diminished energy levels,cancers, damage to blood composition, lungs, kidneys, liver, and othervital organs, and even death. Other heavy metals of concern includeantimony, chromium, cobalt, copper, manganese, nickel, uranium,vanadium, and zinc.

It is therefore necessary for manufacturers to treat these industrialwastewater streams to reduce these heavy metals to acceptable levelsbefore they are introduced into water streams and water bodies that aresubject to environmental government laws and regulations. As a result ofimproper treatment prior to discharge, many heavy metals have been foundto exist at harmful levels in ground waters which are destined forpotable drinking water. Agricultural, meat packing, mining, andhydrofracking industries also face particular risks of waste watercontamination.

A “solution” represents a mixture of two or more individual substancesthat cannot be separated by a mechanical means, such as filtration. Forexample, a liquid solution occurs when a liquid, solid, or gas solute isdissolved in a liquid solvent. The liquid solution constitutes anaqueous solution if the solvent is water. Wastewater streams very oftenconstitute aqueous solutions containing one or more contaminants.

Chemical Water Treatment Methods

Chemical treatment methods are known in the industry for processingwastewater streams. In one common method, the wastewater is treated witha caustic agent like hydroxide to adjust the pH of the water so that themetals form insoluble precipitates. A coagulant in the form of anorganic ferric chloride or ferrous sulfate is then added to the water topromote settling of the metal hydroxide precipitates. The precipitateparticles settle into sedimentation tanks. A filtration medium likesilica sand, diatomaceous earth, carbon, or cloth is then used tocapture the remaining metal hydroxide found in the water. But, thisprocess requires very large volumes of chemicals, as well asland-filling or treatment of the resulting toxic metal sludges.

Non-Chemical Water Treatment Methods

Non-chemical treatments of wastewater generally employ a mechanism knownas “sorption.” Sorption can involve both chemical and physicalprocesses, but the end result is the transfer of a substance from onephase to another. In other words, sorption is the movement of toxins andcontaminants from the dissolved, aqueous phase to the surface of a solidmedia. Three different types of sorption predominate wastewatertreatment technology: ion-exchange, absorption and adsorption.

Ion exchange is a separation process widely used in the food andbeverage, hydrometallurgical, metals finishing, chemical andpetrochemical, pharmaceutical, sugar and sweetness, ground and potablewater, nuclear, softening and industrial water, semiconductors, power,and many other industries. Aqueous and other ion-containing solutionscan be purified, separated, and decontaminated by swapping targeted ionscontained in the solution with substitute ions typically provided by ionexchange resins or other substrates.

But ion exchange is also a proven technology for removing dissolvedmetals or other impurities from these wastewater streams. It representsa reversible process in which the ionized metal or other impuritycompound or element changes place with another ionized compound orelement on the surface of a medium like an ion exchange resin.

Ion exchange can produce high-purity water (including softening,deionizing, water recycling, and removal of heavy metals) from thewastewater. In a familiar example to many readers, an ion exchange-basedwater softener works by passing hard water naturally containing anabundance of calcium and magnesium cations through a volume of resinbeads containing sodium ions on their active sites. During contact, thecalcium and magnesium cations will preferentially migrate out ofsolution to the active sites on the resin, being replaced in solution bythe available sodium ions. This process reaches equilibrium with a muchlower concentration of calcium and magnesium cations in solution,thereby “softening” the water. The resin can be recharged periodicallyby washing it with a solution containing a high concentration of sodiumions, such as a sodium chloride solution. The calcium and magnesiumcations accumulated on the resin will migrate off it, being replaced bythe sodium ions from the salt solution until a new equilibrium state isreached.

Synthetic ion exchange resins are typically used within ion exchangeprocesses. These synthetic resins commonly are formed of small 0.03-2.0mm beads made from an organic polymer substrate, such as cross-linkedstyrene and divinylbenzene copolymers. Moreover, these resin beads willfeature a highly developed structure of pores on the surface of theresin, which provide the sites for trapping and releasing ions. Theseresin beads can be converted to cation-exchange resins throughsulfonation, or to anion-exchange resins through chloromethylation.

In wastewater treatment, these ion exchange resins remove the heavymetals from the solution, and replace them with less harmful elementslike potassium or sodium. But, this process for producing syntheticresins is expensive. The resin beads are also highly susceptible to“fouling.” While soluble organic acids and bases removed by thesynthetic ion-exchange resin are shed during regeneration, non-ionicorganic materials, oils, greases, and suspended solids also removed fromthe water tend to remain on the surface of the resin bead. Foulants canform rapidly on the resin, and can significantly hinder performance ofthe ion-exchange system. Cationic polymers and other high molecularweight cationic organics are particularly troublesome at anyconcentration. For certain types of resins, even one ppm suspendedsolids can cause significant fouling of the resin beads over time. Thus,a prefiltration unit in the form of activated carbon or other separationmaterial may need to be positioned upstream of the ion-exchange unit toremove these organic contaminants before the wastewater is passedthrough the ion exchange resin, further complicating the water treatmentprocess and its costs. The costs associated with this pretreatment canbe substantial.

Additionally, resins require regeneration once the ion-exchange sitehave been exhausted, for example, as feedwater flows through a bed.During regeneration of a cationic resin, metal cations that werepreviously adsorbed from the wastewater flow, are replaced on the resinbeads by hydrogen ions. A step known as “backwash” is often employedduring regeneration, so that any organic contaminant buildup in theresin can be relieved, thereby allowing free flow of the wastewaterthrough the resin beads. But, chemically-regenerated ion-exchangeprocesses known in the art tend to use excessive amounts of regenerationchemicals, which require periodic and even on-going treatment, as wellas safe disposal of the chemical waste. These processes can be complexand expensive to operate.

Another “sorption” separation process is absorption. This is a physicalor chemical phenomenon or process in which atoms, molecules, or ionsenter some bulk phase, whether it be a gas, liquid, or solid material.The gas, liquid or solid material takes in the other substance, like asponge soaking in water. But absorption is necessarily limited by thephysical capacity of the absorbent substrate, and can require frequentpurges of the taken-up substance to replenish the absorbent capacity ofthe substrate.

Yet another sorption process is adsorption. This represents a process inwhich atoms, ions, or molecules from a gas, liquid, or dissolved solidadhere to the surface of a substrate. This constitutes a surface-basedseparation process, instead of absorption which involves the wholevolume of the substrate material. Like ion exchange, in adsorptioncertain adsorbates are selectively transferred from the fluid phase tothe surface of insoluble, rigid particles.

Activation of Carbon-Based Media

“Activation” is the process of treating a material that is high incarbon for purposes of increasing surface area and creating porosity.Materials can be activated either with chemical treatment followed by athermal step, or with heat treatment alone. Most commonly, carbonmaterials that have been activated then undergo further chemicaltreatment in order to change the activity of the surface of thecarbon-based material.

Activated carbon substrates have been employed in the water filtrationindustry for this adsorption separation process. Unlike syntheticpolymer resins used in ion exchange processes, these activated carbonmaterials constitute a form of carbon that has been processed to make itextremely porous with a resulting very large surface area for adsorptionof impurities via van der Waals forces or London dispersion forces, orchemical reactions. Due to its high degree of microporosity, just onegram of activated carbon substrate can provide a surface area exceeding500 m² (about one tenth the size of a football field). Moreover, suchactivated carbon materials can be produced from a variety of naturalorganic materials like vegetable matter, soft woods, cornstalks,bagasse, nut hulls and shells, various animal products, lignite,bituminous, or anthracite coals, straw, petroleum pitch, or peat.

Chemical Activation

When some of the energy required for a reaction is provided by apreceding exothermic chemical reaction, there is said to be a “chemicalactivation.” Carbonaceous material may be chemically activated byimpregnating it with an acid, strong base or a salt like phosphoricacid, sulfuric acid, potassium hydroxide, sodium hydroxide, calciumchloride, or zinc chloride, followed by carbonization via pyrolysis at ahigh 450-900° C. temperature range. For example peat can be impregnatedwith phosphoric acid or zinc chloride mixed into a paste, and thenpyrolyzed at 500-800° C. to activate the peat, followed by washing,drying, and grinding this chemically activated peat into a powder toproduce activated carbon having a very open porous structure that isideal for adsorption of large molecules.

For example, Soviet Published Patent Application No. 1,142,160 filed bySokolov et al. discloses an active adsorbent product made from aluminumsalt sludge. Organo-aluminum sludge produced in the process ofcoagulation of aluminum salts in water is thickened to create aconcentration of 10-17%. The aluminum hydroxide fraction is used toprecipitate out the organic compounds during a process that is calledcoagulation. The aluminum hydroxide and organic compounds are thentreated with sulfuric acid, and then the solid phase is heated at210-270° C. for 2-4 minutes. This process destroys the organic materialto convert it into activated carbon, and some portion of organicmaterial is reacted with sulfuric acid to produce sulfonic acidderivatives. The end product is used to remove organic compounds andmetal cations (e.g., nickel and cobalt) from waste water. But, not onlydoes Sokolov use a non-natural starting material, but also he reliesupon a combination of chemical activation to produce activated carbon,and chemical modification to produce the SO₃ ⁻ groups on the surface ofthe product necessary for yielding its cation-exchange properties.

Physical Activation

Alternatively, carbonaceous sources such as coconut hulls or bamboo canbe physically activated by exposing it to an oxidizing atmosphere likecarbon dioxide, oxygen, or steam at a very high temperature falling withthe 650-1200° C. range. These processes for producing activated carbondo not produce a media with a usable ion-exchange capacity. As anexample, U.S. Pat. No. 6,316,378 issued to Giebelhausen et al. disclosesthe manufacture of shaped activated carbon pellets. Polymer resin,acetylene coke, or pearl cellulose are dried at 250-300° C. ThenGiebelhausen carbonizes his material at a very high 850-880° C.temperature without steam. Finally, he thermally activates his carbonpellet product at an even higher 910-915° C. temperature in a hotgas-fired kiln. Steam is used by Giebelhausen merely to preventexplosions.

In another example, U.S. Published Application 2003/0041734 filed byFunke et al., shows a method for producing an ultra-low emission (“ULE”)carbon material. The Funke reference explains that conventionalactivated carbon materials contain too much water and carbon dioxideconstituents to effectively adsorb water and carbon dioxide moleculesfrom a gas stream in need of purification. Therefore, Funke subjectsactivated carbon with no ion exchange capacity to extremely hightemperatures and time in a reactor in order to drive off all the H₂O andCO₂ molecules from the activated carbon, This “preconditioned” ULEcarbon material is then further treated to a second activation processunder the flow of an ultra-dried reactive purge gas like ammonia toremove any additional moisture from the ULE carbon material. Devoid ofH₂O and CO₂ molecules, this processed carbon material can readily adsorbnew H₂O and CO₂ molecules from the gas stream by simple adsorptionwithout any ion exchange reaction. Furthermore, such treatmentconditions are on the order of 500-700° C. for 24 hours to 5 days.Indeed, these are extreme conditions that in no way resemble normalphysical activation.

Pyrolysis of Peat

“Pyrolysis” is related to activation in that material high in carboncontent is exposed to heat. Activation often involves pyrolysis, but theend result is to produce a product with increased surface area.Pyrolysis constitutes the decomposition of organic material throughheating, and it occurs in an oxygen-free environment.

Peat is a substance that can be pyrolyzed, and comparative studies ofthe pyrolysis kinetics for coal and peat have been performed. SeeDurusoy et al., “Pyrolysis Kinetics of Blends of Gediz Lignite withDenizli Peat,” Energy Sources, vol. 23, pp. 393-99 (2001). But, noparticular temperature ranges for pyrolysis were determined in thisstudy, nor was any ion-exchange medium prepared.

Common uses of Activated Carbon

Activated carbon filters are popular for home and small-volume waterpurification systems, because of the absorbency of the carbon substance.Activated carbons are known to have a heterogeneous pore structure,which is classified as microporous (diameter of pore <2 nm), mesoporous(diameter of pore between 2-50 nm), and macroporous (diameter ofpores >100 mm). Activated carbons have a large adsorption capacity,preferably for small molecules, and are used for purification of liquidsand gases. Volatile organic chemicals found in the water are removed viaadsorption. But, activated carbon filters are generally not successfulin removing dissolved metals like antimony, arsenic, barium, beryllium,cadmium, chromium, copper, mercury, nickel, and selenium from the water.Moreover, the purification efficiency of activated carbon filters isdirectly influenced by the amount of carbon contained in the filterunit, the amount of time that the water-borne contaminant spends incontact with the carbon, and the contaminant particle size. Hence,activated carbon filters must necessarily contain very large carbonvolumes treating very low water flow rates, which makes themcomparatively unsuitable for processing industrial wastewater streams.

Peat-Based Sorption Media

It would therefore be desirable to produce a sorption medium from anatural, organic material. However, a balance must be struck between thephysical integrity of the form of the sorption medium versus the abilityof the medium to serve as an ion-exchanger, adsorbent, or absorbent.Partially decomposed organic starting material like peat inherentlypossess ion-exchange and adsorbent characteristics. Peat is composedmainly of marshland vegetation, trees, grasses, fungi, as well as othertypes of residual organic material such as insects and animal remains,and is inhibited from decaying fully by acidic and anaerobic conditions.It is also abundant in many places in the world. For example, 15% ofMinnesota is covered by valuable peat resources, comprising 35% of thetotal peat deposits found in the lower 48 states in the U.S.

Pellets made from peat are known within the industry. For example, U.S.Pat. No. 6,455,149 issued to Hagen et al. discloses a process forproducing peat pellets from an admixture of peat moss, pH adjustingagent, wetting agent, and other processing additives. The resultinggranules can be easily broadcast spread on the ground, and returned totheir original peat moss form upon wetting to act as a fertilizer. Noeffort is made by Hagen to activate his pellets to prepare theadsorption or absorption or ion exchange characteristics of theirsurface, nor are they used as an ion exchange medium. U.S. Pat. No.3,307,934 issued to Palmer, et al. shows another fertilizer productcontaining peat, and water-soluble inorganic fertilizer salt likediammonium phosphate, sulfate of potash, or urea. This peat productlikewise is not activated, nor is it used as an ion-exchange oradsorption medium. Instead, Palmer uses peat merely as a carrier for hisfertilizer salt.

It is also known in the wastewater treatment industry to use pelletsmade from natural organic materials as a pollution filtering medium. Forinstance, U.S. Pat. No. 5,624,576 issued to Lenhart et al. illustratespellets made from leaf compost, which are then employed to removepollutants from storm water. U.S. Pat. No. 6,143,692 issued to Sanjay etal. discloses an adsorbent made from cross-linked solubilized humicacid, which can be employed for removing heavy metals from watersolutions. U.S. Pat. No. 6,998,038 issued to Howard contains a detaileddisclosure of a storm water treatment system for which the filteringmedia can include peat. U.S. Pat. No. 6,287,496 issued to Lownds shows aprocess for preparing peat granules using a binder and gentle extrusion.In U.S. Pat. No. 5,578,547 issued to Summers, Jr. et al., a mixermachine and process for producing peat beads for adsorption of metalcations at dilute concentrations (<10 ppm) is disclosed. Peat and asodium silicate or polysulfone/methylene chloride binder are fed to themixer to form a pellet, followed by drying. This binder chemical actslike a glue to fuse the peat fibers together in order to create astronger peat pellet. Summers fails to disclose or suggest any thermalactivation process step. See also U.S. Pat. No. 5,602,071 issued toSummers, Jr. et al.

Russian Patent No. 2,116,128 issued to Valeriy Ivanovych Ostretsovteaches a process for producing a peat sorbent useful for removing oilspills from solid and water surfaces. The peat material is dried from60% moisture to 23-25% moisture, and then compressed at 14-15 MPapressure into briquettes. Next, these peat briquettes are heated at250-280° C. without the use of additional hydrophobic chemicals andwithout air. The humic and bitumen fractions within the peat mobilize tothe surface of the peat briquettes to produce a natural hydrophobiccoating. This hydrophobic coating is necessary for the peat briquettesto be able to soak up oil. Ostretsov also reduces the moisture of hisheat-treated peat briquettes all the way down to 2.5-10% wt. moisture.This significant water reduction assists with the hydrophobic coatingformation and frees up the pores in the peat material so that they areavailable to soak up oil. Unfortunately, Ostretsov's aggressive thermaltreatment of his peat material will reduce hardness, but he does notneed to worry about hardness in his peat briquettes, because he does notforce water through the briquettes under pressure during waste watertreatment. Instead, he merely floats his peat briquettes on the watersurface to soak up the oil spill. Indeed, this is not an ion-exchangemedium.

Russian Patent No. 2,173,578 also issued to Ostretsov discloses asimilar peat sorbent product useful for soaking up oil spills on watersurfaces. His peat under this patent disclosure is milled at lowdecomposition and dried to 20-48% moisture, and then compressed underpressure at a force below 10 MPa, and then heated under a carbon dioxideblanket without oxygen for 20-90 minutes “at a temperature of 15-30° C.above the exuding temperature of water-insoluble resins of the carrier.”However, it is clear that Ostretsov's process will produce a hydrophobiccoating on the surface of his peat material, which is the opposite ofthe hydrophilic surface that is required for adsorption of metal cationsfrom waste water streams.

Peat is a substance that can be pyrolyzed, and comparative studies ofthe pyrolysis kinetics for coal and peat have been performed. SeeDurusoy et al., “Pyrolysis Kinetics of Blends of Giediz Lignite withDenizli Peat,” Energy Sources, vol. 23, pp. 393-99 (2001). But, noparticular temperature ranges for pyrolysis were determined in thisstudy, nor was any ion-exchange medium prepared.

Peat as an Ion-Exchange Media

Various efforts have been made to prepare ion-exchange mediums from peatstarting material which is chemically activated and, in some cases,chemically modified before the chemical activation step. For instance,U.S. Pat. No. 4,778,602 issued to Allen, III teaches a multi-functionalfiltering medium consisting of highly humified peat which is treatedwith an alkaline solution to hydrolyze the humic and fulvic acidfractions contained therein. Next, the peat product is treated with aquaternary amine solution to precipitate out the hunmic and fulvic acidfractions from the peat. After filtering the drying the peat cake,nitric acid or sulfuric acid is added to neutralize the amine tochemically modify the peat to increase its cation exchange sites byeither adding SO₃ ⁻ groups to the peat surface structure, or to oxidizethe organic carbon to improve the cation capacity. Finally, the peatresidue may be treated to a semi-coking process step at 200-1000° C. ata 40 psi pressure, thereby allowing carbonization of peat residue. Thiswill actually destroy the carbon fibers. Thus, Allen actually chemicallymodifies his peat product to increase the cation exchange sites,followed by chemically activating it to increase hydrophobic adsorptionproperties. The enhanced cation exchange capacity is also aided bydestruction of the carbon fibers via the semi-coking (pyrolyzation)step.

U.S. Pat. No. 6,042,743 issued to Clemenson discloses a method forprocessing peat for use in contaminated water treatment. Clemenson mixesraw peat with heated sulphuric acid to produce sulfonated peat slurry.After cooling and drying the slurry admixture to a 60-70% moisturecontent, he adds a binder like bentonite clay to coagulate the acidicpeat slurry, extrudes pellets, and then bakes the sulfonated peatpellets in an oven at 480-540° C. This baking step drives off themoisture, but it also destroys the carboxylic acid (CHOOH) groups. Hischemical activation of the peat material via the sulfonation step addssulfonate groups (—SO₃ ⁻) to the resulting peat granules. In use,Clemenson's peat pellets adsorb metals by attaching the metal cations tothe sulfonic groups due to their opposite charged states. Clemensonchemically modifies the surface of peat, but failed to preservecarboxylic groups (COOH) that naturally occur in peat. See also U.S.Pat. No. 6,429,171 issued to Clemenson.

In yet another example, U.S. Pat. No. 5,314,638 issued to Morinediscloses a chemically modified peat product that can be used as anion-exchange material. This peat material is air dried and milled to asize of one mm or less; hydrolyzed in an aqueous hydrochloric acidsolution to remove the soluble components (sulfuric acid and nitric acidmay also be used); further treated in an extractor with2-propanol/toluene solvent to remove the solvent-soluble bitumen; driedto remove the residual solvent; and then immersed in a hot concentratedsulfuric acid bath at 100-200° C. for 1-4 hours. This is achemically-modified peat product. The hot sulfuric acid bath processstep comprises chemical modification in which the sulfuric acid reactswith the peat fibers to add sulfonate anions (SO₃ ⁻) to its surface.These anions within the ion-exchange resin attract metals via chemicalattachment.

Various efforts have been made within the industry to use granulated anddried peat material as a cation exchange media. More particularly,Soviet Published Patent Application No. 806,615 filed by PeterIllarionovich Belkevich et al. produces a water filter product frompellets comprising a paste made from peat and a precipitate ofneutralizing etching solution. This paste and the resulting pellets areproduced without any physical activation treatment. Moreover, Belkevichuses his neutralizing etching solution like a glue to hold the peatfibers together in a pellet and therefore obtain the desired granulehardness. Furthermore, Belkevich employs his peat pellets as a filter toremove non-ferrous metals like copper and zinc and petrochemicalproducts from waste water. It is unclear that Belkevich's peat pelletsare acting as an ion-exchange material.

Challenges Faced by Peat and Other Natural Organic Materials

But, the large body of available research illustrates the underlyingshortcomings for natural peat. In its natural form, peat has lowmechanical strength, tends to shrink and swell, and does not allow forhydraulic loading. Moreover, peat and other organic starting materialssuffer from a number of other problems that compromise their utility asa sorption medium. For example, prior art activation steps likepyrolysis can cause these materials to lose their ion-exchange capacity.Carbonization may cause considerable shrinkage and weight loss of thematerials, as well as loss of natural adsorption properties toward metalions. Organic sources also generally suffer from non-uniform physicalproperties. Naturally occurring organic ion exchange media are unstableoutside a moderately neutral pH range. Finally, such natural organic ionexchange media tend to be prone to excessive swelling and peptizing, andleaching naturally occurring heavy metals into the treated wastewatersolution.

While the processes known in the art for the preparation of sorptionmaterial sourced from natural solid organic material like activatedcarbon have been useful for certain limited adsorption applications, formany other applications it will be necessary to increase the hardness ofthe ion exchange medium, while minimally sacrificing the media'scation-exchange capacity in the process, and minimize leachingnaturally-occurring heavy metals into the treated wastewater solution.It is therefore necessary to develop a low-cost process for producingion-exchange and adsorption media sourced from natural organic startingmaterial exhibiting good natural ion-exchange capacity, increasedadsorption capabilities towards heavy metals, eliminate leachingnaturally-occurring inorganic and organic compounds, and improvedstrength so that the medium can be utilized in a wider range of end-useapplications, including the removal of heavy metals from industrialwastewaters. It would also be useful to be able to prepare such asorption media using low processing temperatures without the use ofchemical activation with its caustic and corrosive chemicals, andchemical modification with its reliance upon the addition of functionalgroups to the media to enhance its ion-exchange capacity. Likewise, itwould be beneficial to avoid the aggressive chemical modification of thepeat or other organic starting material substrate before the chemicalactivation step.

Even if a peat or other organic material granule could be produced withappropriate characteristics of hardness and ion-exchange capacity, apercentage of the natural active sites on the media could potentially befilled as a result of the environment of the parent material. In otherwords, organic materials tend to bond with contaminants in environmentalwaters. For example, Minnesota peats are often loaded with manganese asa result of the geology and hydrology of their sites. This means thatpotentially manganese and other metals that naturally exist within,e.g., peat can leach back into the wastewater during the ion-exchangeprocess, thereby leaving the wastewater stream with a new form ofunwanted contamination. Therefore, it would be beneficial to produce aprocess that can chemically treat the granules after any thermalactivation step to reduce the levels of manganese and othernaturally-occurring metals within the peat that can leach into thewastewater, while increasing the ion-exchange performance and adsorptioncapabilities by different mechanisms of the granule or pellet forremoving heavy metals. U.S. Pat. No. 4,671,802 issued to Jönsson doesdisclose a chemically-enhanced peat product. The peat material ispretreated with H₂SO₄ at pH=3 to protonate the carboxylic acid groups toneutralize the negative charges on the peat surface. A cationicpolyelectrolyte of polyamines and polyamide derivatives is then added tobind the peat particles together. Metal salts can be added to reduce theamount of polyelectrolytes required. The peat material is then heated ata high temperature to dry it, and it is then subjected to dewatering ina mechanical press. Thus, this in actuality constitutes a chemicalprocess for eliminating the repulsive forces along the peat surface.

A comparative experiment using peat chemically treated by NaOH or NaClis disclosed within Corneliu Caramalau et al., “Kinetic Study of Cobalt(II) Adsorption on Peat Activated by Simple Chemical Treatments,”:Environ mental Engineering & Management Journal, vol. 8, no. 6, pp.1351-58 (2009). The peat was dried, ground, sized, and then treated withan aqueous 0.2 M solution of H₂SO₄, NaCl, or NaOH for 60 minutes. Thematerials were then used to treat cobalt solutions, and the resultscompared. The researchers found that there was no real change in thepeat particles treated with NaCl solution. The NaOH solution causedcarbonyl compounds and undissociated carboxylic acid groups to disappearfrom the peat surface. It changed the peat surface by hydrolyzation, butit will ruin the strength of the granule, and increase the biologicaloxygen demand of the cobalt solution. The cobalt adsorption capacity ofthe chemically-treated peat increased for NaOH (+28.05%) and NaCl(+12.32%), while decreasing for H₂SO₄ (−10.79%), the high initial cobaltconcentration present in the aqueous solutions diminishes theimpressiveness of this 12% value. The researchers found that treatmentwith NaOH has a greater effect to increase the adsorption capacity ofpeat, compared to treatment with NaCl, which will discourage researchersfrom using salt solutions and solutions of acids to increase theadsorption capacity and activity of peat. There is also a lack ofinformation or influence for the proposed treatment on thenaturally-occurring heavy metals contaminants in the peat.

SUMMARY OF THE INVENTION

A process for preparation of a granulated or pelletized sorption mediumfrom a partially decomposed organic material like peat, followed bylow-temperature thermal activation of the sorption medium to produce ahigh degree of granule or pellet hardness balanced against anefficacious level of ion-exchange and adsorption capacity, followed bychemical treatment of the sorption material via an acid solution and asalt solution to increase the availability of naturally-occurring activesites in the granules or pellets to enhance their ion-exchange,complexation, chelation, and adsorption performance, while minimizingthe leaching of contaminants like metals and organic molecules found inthe sorption medium to an aqueous solution is provided by thisinvention. The sorption medium of this invention can be used in avariety of aqueous solution treatment processes, such as wastewatertreatment for removing heavy metal constitutes via ion-exchange andcomplexation mechanisms, and also reducing the levels of manganese,iron, and other naturally-occurring metals found in the peat substratefrom leaching back into the waste water.

In another embodiment of the sorption medium of the present invention, aspecially preselected solution of soluble salts may be used for the saltsolution used to chemically treat the sorption material, so that when itis used as an ion exchange type medium for treating an aqueous solutionlike waste waters, the preselected cations from the solution of solublesalts placed on the active sites of the partially decomposed organicmaterial in the sorption medium will alter the coefficient that definesthe equilibrium and increase the adsorption capacity more in favor ofadsorption of major toxic metals found in the waste water at the expenseof less toxic metals found in higher concentrations in the waste water.This allows the end user to target the major toxic metals for adsorptionby the sorption medium containing the cations contributed by thepreselected solution of soluble salts.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 represents a schematic view of the portion of the process of thepresent invention for preparing the thermally activated peat granule.

FIG. 2 represents a schematic view of the portion of the process of thepresent invention for chemically treating the thermally activated peatgranule by means of an acid solution followed by a salt solution toreduce the presence of unwanted minerals within the peat complex, whileincreasing the sorption capacity and activity of peat granules.

FIG. 3 represents a graphical depiction of comparative adsorption datafor the non-chemically treated, thermally-activated peat granules(APTsorb II) and its chemically-treated counterpart material (APTsorbIII).

FIG. 4 represents a graphical depiction of the effluent concentration ofcadmium at different flow rates in a bed.

FIG. 5 represents a graphical depiction of the effluent concentration ofmanganese at different flow rates in a bed.

FIG. 6 represents a graphical depiction of the cadmium adsorption froman effluent aqueous solution stream containing only cadmium cationsusing a sodium-loaded sorption medium of the present invention.

FIG. 7 represents a graphical depiction of the cadmium and zincadsorptions from an effluent aqueous solution stream containing bothcadmium and zinc cations using a sodium-loaded sorption medium of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A process for preparation of a granulated or pelletized sorption mediumfrom a partially decomposed organic material like peat, followed bylow-temperature thermal activation of the sorption medium to produce ahigh degree of granule or pellet hardness balanced against anefficacious level of ion-exchange and adsorption capacity, followed bychemical treatment of the sorption material via an acid solution and asalt solution to increase its ion-exchange and adsorption performancewhile minimizing the transfer of natural impurities found in thesorption medium to an aqueous solution is provided by this invention.The sorption medium of this invention can be used in a variety ofaqueous solution treatment processes, such as wastewater treatment forremoving heavy metal constituents via ion-exchange and complexationmechanisms, and also reducing the levels of manganese, iron, and othernaturally-occurring metals found in the peat substrate from leachingback into the waste water.

In another embodiment of the sorption medium of the present invention, aspecially preselected solution of soluble salts may be used for the saltsolution used to chemically treat the sorption material, so that when itis used as an ion exchange type of medium for treating an aqueoussolution like waste waters, the preselected cations from the solution ofsoluble salts placed on the active sites of the partially decomposedorganic material in the sorption medium will alter the coefficient thatdefines the equilibrium and increase the adsorption capacity more infavor of adsorption of major toxic metals found in the waste water atthe expense of less toxic metals found in higher concentrations in thewaste water. This allows the end user to target the major toxic metalsfor adsorption by the sorption medium containing the cations contributedby the preselected solution of soluble salts.

For purposes of this invention, “partially decomposed organic material”means natural occurring, carbon-based, organic materials that havepartially decayed or decomposed over time in the ground, or are plant oranimal-based products that are subjected to a bacterial or thermaldecomposition process to partially decompose the organic materialstherein. Such partially decomposed organic material cover a variety ofsubstances including without limitation compost media (e.g., leafcompost media, peat, plant by-products and combinations thereof),livestock manure, sewage sludge, lignite coal, partially decomposedwood, apatite (calcium phosphate), zeolites, and combinations thereof.Such partially decomposed organic material must also exhibit anion-exchange capacity between 5-200 mEq per 100 g of organic material,as measured by Barium Acetate Procedure. Compost media is any decayedorganic matter. Plant by-products may include partially decomposedplants, leaves, stalks, and silage, for example. Livestock manure is thedung and urine of animals. Sewage sludge is solid, semi-solid, or liquidresidue generated by the processes of purification of municipal sewage.Each of the foregoing sources of decomposed or partially decomposedorganic matter has innate ion-exchange capacity.

As used in this Application, “aqueous solutions” means any water-basedsolution containing an environmental impurity as a solute produced bymanufacturing, agricultural, or mining industries or populationcommunities. Examples include, without limitation, wastewaterdischarges; industrial streams; storm water runoffs; mine dewateringstreams from mining pits; animal slaughterhouse, cattle-yard, and otheragricultural runoffs; spent processing waters emanating from mining,grinding, milling, metallurgical, or extraction process; andhydrofracking.

For purposes of this invention, “impurities,” “contaminants,” or“aqueous contaminants” means any chemical element or compound found inan aqueous solution that poses a health risk to humans or animals, or isotherwise subject to environmental laws or regulations, includingwithout limitation heavy metals like arsenic, lead, mercury, cadmium,manganese, iron, zinc, nickel, copper, molybdenum, cobalt, nickel,chromium, palladium, stannum, or aluminum; radioactive materials likecesium or various isotopes of uranium; sulfates, phosphorous, selenium,boron, ammonia, refrigerants, and radon gases.

The term “media contaminants” means any chemical element or compoundfound in the partially decomposed organic material that poses a healthrisk to humans or animals, or is otherwise subject to environmental lawsor regulations. Examples include metals like manganese, iron, calcium,or barium, or organic molecules that can leach from the partiallydecomposed organic material into treated wastewater.

As used in this Application, “particles” includes anythree-dimensionally hardened shaped product formed from the partiallydecomposed organic material, including, without limitation, granules orpellets.

The term “mEq” means milliequivalents. The equivalent is a common unitof measurement used in chemistry and the biological sciences. It is ameasure of a substance's ability to combine with other substances. Theequivalent entity corresponding to the transfer of a H⁺ ion in aneutralization reaction, of an electron in a redox reaction, or to amagnitude of charge number equal to 1 in ions. One Eq of a substance isequal to one more divided by the valence of the substance (i.e., thenumber of electrons that the substance would engage in participating inthe reaction). Because, in practice, the equivalent is often very small,it is frequently described in terms of milliequivalents (mEq). A mEq is1/1000 of an equivalent.

The term “hardness” means a property of the granule medium's ability toresist attrition during handling and operation. The “hardness number” isa measure of this property and is determined by way of the “Ball-PanHardness” test. The higher the value, the less the losses in uses. Acertain amount of material is put into a pan, together with some steelballs, and shaken for a defined period of time. The material is weighedbefore and after the shaking to determine the amount of attrition. Thepercent of original material that remains after shaking is the “hardnessnumber.”

The terms “empty bed contact time” means the time required for a liquidin a carbon adsorption bed to pass through a carbon column, assuming allliquid passes through at the same velocity. It is equal to the volume ofthe empty bed divided by the flow rate.

The term “sorption” means a variety of chemical mechanisms for removinga chemical element or chemical compound from an aqueous solution,including cation-exchange, complexation, chelation, adsorption, orabsorption.

The term “about” means approximately or nearly, and in the context of anumerical value or range set forth herein means=2% of the numericalvalue or range recited or claimed.

The term “μg” means microgram or one-millionth of a gram or one one-onethousandth of a milligram.

The term “ng” means nanogramis or 1×10⁹ grams or 0.000000001 grams.

As used within this Application, “major toxic metals” means any chemicalelement or compound found in an aqueous solution that poses a healthrisk to humans or animals, or is otherwise subject to environmental lawsor regulations, including without limitation heavy metals like arsenic,lead, mercury, cadmium, manganese, iron, zinc, nickel, copper,molybdenum, cobalt, nickel, chromium, palladium, stannum, or aluminum;radioactive materials like cesium or various isotopes of uranium;sulfates, phosphorous, selenium, boron, ammonia, refrigerants, and radongases.

For purposes of this application, “more innocuous metals” means anychemical element or compound found in an aqueous solution that does notnecessarily pose a health risk to humans or animals or is otherwisesubject to environmental laws or regulations, including withoutlimitation metals like magnesium, beryllium, strontium, barium, calcium,manganese, copper, zinc, iron, lead, potassium, lithium, as well asammonium and ammonium groups.

While the sorption medium of the present Application is described usingpeat as the partially decomposed organic matter starting material, itshould be understood that the invention is not limited to peat-basedsorption material. Likewise, the end-use applications for the sorptionmedia of the present invention extend well beyond the treatment of heavymetals in wastewater streams described in this Application. For example,the sorption media of the present invention can also be used to removesulfates, phosphates, and radio-nucleotides from aqueous solutions. Theycan also serve as solid-phase extraction tools, as well as a chemicaluseful in the mining industry for concentrating copper.

Production Process for Thermally-Activated Sorption Material

The process for preparing the sorption medium product 10 of the presentinvention is depicted in FIG. 1 where peat is used as the startingpartially decomposed organic material 12. A variety of different typesof peat may be used for purposes of this invention, including withoutlimitation, reed sedge, sphagnum peat, high moor peat, transitionalmoor, and low moor peat. The peat material should be dug from the groundand used in its natural state without any further decomposition processsteps. It may, however, be cleaned to remove sticks, stones, and otherforeign debris from the fibrous peat material.

Next, the peat material 12 is adjusted for acidity to a pH range ofabout 6.4-7.0. Finely ground calcium carbonate may be admixed into thepeat material for this purpose. Such calcium carbonate should preferablyhave a particle size of about minus 325 mesh. It should be admixed on aweight ratio basis of about 1-5%, preferably 2%, with the peat material12.

The substantially neutralized peat material 14 is then introduced to agranulating machine 16, such as one sourced from Andritz, Inc. ofBellingham, Wash. The loose, substantially neutralized fibrous peatmaterial 14 will be tossed around inside the drum of the granulator tocause the fibers to adhere to each other, and build up granules ofdesired size. A binder additive like lignosulfonate may be optionallyadded to the peat material in the granulator drum to assist thisgranulation process.

Alternatively, the loose, substantially neutralized peat material 14 maybe introduced to an extruder. This extruder will apply pressure to thefibrous material to produce pellets of desired size. Such an extrudermay be sourced from J.C. Steele & Sons of Statesville, N.C.

Next, the peat granules or pellets 16 are sent to a dryer 18 such as abelt or rotary dryer sourced from Harris Group of Atlanta, Ga. Usingdirect heat, the peat granules or pellets will travel through the lengthof the dryer having an inlet temperature of about 400° C. and an outlettemperature of about 80° C., so that the natural 40% wt moisture levelof the peat material contained in the peat granules or pellets will bereduced to about 10-14% wt moisture. Thus, this drying step 18 should becarried out across a temperature range of about 80-400° C. with thepreferred temperature of exposure being about 90° C. for about 45minutes.

The resulting dried peat granules or pellets are then crushed andscreened to an appropriate size of about 6 mesh×30 mesh to 30×100 mesh.

The dried peat granules or pellets 18 are then introduced to a thermalactivation step 20, also known as “torrefaction.” The peat granule orpellet is put in a jacketed ribbon mixer that has thermal fluid like oilcirculating through the jacket. The ribbons are fitted with “lifters,”which pick up the granular peat and drop it through the atmosphereinside the ribbon mixer. This exposure to the hot, inert atmosphere iscritical to bringing the granule up to temperature as quickly aspossible.

During this heating process, a unique combination of time andtemperature are critical for the production of the thermally-activatedpeat granule (called “APTsorb II” within this Application). Activation(IUPAC Recommendations 1996) can be defined as input of external energyinto a chemical system to bring about activation of the system. Thisactivation will initiate or expedite thermochemical reactions. In theinstance of this APTsorb II peat granule, heat as a form of energy isfirst provided by the thermal fluid circulating in the ribbon mixer.This heating process results in the chemical reaction-decomposition ofhemicellulose, which occurs naturally in partially decomposed plantmatter such as peat. The decomposition of hemicellulose is itselfexothermic, as evidenced by a continuing rise in atmospheric temperatureeven when the heat input of the thermal fluid is stopped. As itdecomposes and gives off heat, hemicellulose is converted to highlyreactive, cyclic molecules called lactones. Some of these lactonesescape the reaction zone along with moisture, but given the correctstarting temperature and duration, the bulk of the lactones remainwithin the reaction zone and undergo a cross-linking polymerization withthe natural matrix of the peat. This cross-linking reaction is theresult of the exothermic reaction of thermal decomposition ofhemicelluloses. It also is the reaction which results in the hardenedpeat granule called APTsorb II.

The term activation itself has several different meanings and nuances.Activation as described by activated carbon, a common filtration mediafor purification of liquids and gases, is described as pyrolysis andcarbonization of organic material, which is resulted in the increase ofsurface area and can be tightly controlled by reagents and temperatureto create a material with very specific porosities and physicalabsorption activity/capacity. It can be achieved by thermal orchemical/thermal reactions.

Thus, the temperature of the thermal fluid is quickly raised toapproximately 300-320° C., more preferably 304° C., to thermallyactivate the peat granules to increase their hardness. The temperatureinside the mixer slowly rises as volatiles and contained moisture aredriven off. This gasified water and volatile mix constitute the “inert”atmosphere and work to purge air out of the ribbon mixer.

As the temperature in the atmosphere inside the mixer climbs into the216° C. range, the rapid breakdown of hemicellulose begins. This is thesame reaction as torrefaction of wood. This breakdown of hemicelluloseis an exothermic chemical reaction which allows for a rapid rise in thetemperature of the atmosphere inside the mixer. The actual temperatureof the granule is hard to determine but probably is much lower.

The above reaction is allowed to continue as the temperature is driveninto the 271-277° C. temperature range. At this point, the boiler thatis used to heat the thermal fluid is turned off. The above reactionreleases enough heat to maintain the temperature of the atmosphere inthe above range. The process is allowed to continue until approximately20 minutes have passed where the temperature has been maintained above271° C.

In the case of the APTsorb II peat granule, the media is described aspartially activated. This refers to the thermal energy that is deliveredto the peat material to initiate the decomposition of hemicellulose inthe tightly controlled manner that leads to the increase of structuralhardness of the material without losing the natural ability of materialto sorb metal ions. If the reaction were allowed to continue past theprescribed time, the resulting material would continue to gainstructural hardness but would lose its ability for sorption of metals.

This thermal activation process step 20 should preferably be conductedat a temperature inside the activator of about 175-287° C., preferably200-275° C., more preferably 250° C., and a time period of about 25-90minutes, preferably 30-60 minutes, for achieving maximum granulehardness. In order to achieve maximum cation exchange capacity in thepeat granule, the activation step should be conducted for 25-90 minutes,preferably 25-40 minutes. It has been found that 32 minutes representsan optimal compromise as an activation step time duration for achievingdesirable levels of both granule hardness and cation exchange capacity.Note that this activation temperature range is different from the higher300-320° C. oil temperature used to heat the activator. The thermal heatis applied directly to the dried peat granules 18 without any steam,carbon dioxide, nitrogen, or other inert gas media typically used withinthe industry in a physical activation process.

In an alternative embodiment, a thermal carrier like steam, carbondioxide, nitrogen, or other inert gas media can be used in the thermalactivation step 20 to deliver the heat as a form of energy to the peatgranule. The gas should preferably be carbon dioxide, and the peatgranule should be exposed to it for a time period of about 20-90minutes, preferably 40-60 minutes. Unlike the physical activationprocess known in the prior art, this inert gas is not used to oxidizethe surface of the peat granule. Instead, it is merely employed as acarrier gas to improve the application of the heat to the peat granulepursuant to the thermal activation step.

Regardless of which method is used to thermally activate the peatgranules or pellets, the heating process is stopped at this point, andwater is injected in order to rapidly cool the product and stop thereaction. Target moisture for the finished product should be at least10% so as to prevent the thermally activated peat granules from becomingtoo hydrophobic. Danger of fire developing within the bagged product isgreater if finished product is less than 5% moisture content.

This thermal activation results in a hardened media that maintains itsstructural integrity even when wet and retains its affinity for metals.The physical appearance of the APTsorb II peat granule is notsubstantially different from its starting non-thermally-activatedmaterial (called “bioAPT”).

The degree of granule hardness for the resulting thermally-activatedpeat granule 22 of the present invention should have a Ball-Pan Hardnessnumber of about 75-100%. More preferably, this Ball-Pan Hardness numbershould be about 80-98%. Depending upon the specific end-use applicationfor the peat granule 22, a person skilled in the art will be able todetermine the necessary hardness value falling within this range.

The peat granules thermally activated in the manner described in thisApplication will exhibit a copper cation-exchange capacity (“CopperCEC”) of about 120 mEq/100 g of Cu²⁺ at a thermal activation temperatureof about 232° C., while a 287° C. temperature condition produces apartially activated peat granule with a cation-exchange capacity ofabout 92 mEq/100 g of Cu²⁺. Untreated peat has a natural coppercation-exchange capacity of about 120 mEq/100 g of Cu²⁺. Thus,cation-exchange capacity suffers at relatively higher thermal activationtemperatures within the 232-287° C. range, and granule hardness isimproved at activation times up to 60 minutes, while degrading after 90minutes and at temperatures above 287° C. Thus, this invention providesa tradeoff between granule hardness and cation-exchange capacity.

There is significant shrinkage in the actual size of the individualthermally-activated peat granules, so they are screened again across a30 mesh screen. Losses due to shrinkage under the process of the presentinvention are typically 15%.

Without wanting to be bound to any particular chemical theory, it isbelieved that this thermal activation step comprises torrefaction of thepeat granule, which necessarily requires lower temperatures like thepreferred 200-275° C. range identified above. According to a glossary ofterms used in chemical kinetics, including reaction dynamics (IUPACRecommendations 1996), activation can be defined as the input ofexternal energy into a chemical system to bring about activation of thesystem. As commonly understood within the industry, “torrefaction” is amedium-temperature, thermochemical process, commonly carried out around250-300° C., which significantly improves the grindability of wood andstraw. Peat naturally has carbohydrates in it, which undergo athermochemical decomposition to produce lactones, which are then brokendown into hydroxy acids that react with natural polymers found withinthe peat material to cross-link, and as a result to harden the peatgranule. At the same time, this relatively low-temperature range for thethermal activation step will preserve enough of the natural ion exchangecapacity of the peat material to preserve the efficacy of the resultingion exchange medium. This combination of increased peat granule hardnessand preserved ion exchange capacity renders the peat product of thepresent invention an ideal, natural ion exchange medium for removingheavy metal cations from waste water. Thermal activation is normallyapplied in the industry to activated carbon material to increase itssurface area.

Note that this 200-275° C. thermal activation temperature range of thepresent invention is considerably lower than the temperatures normallyassociated with conventional physical activation and chemicalactivation. In the case of physical activation, the starting materialfor, e.g., activated carbon, will first be carbonized by pyrolyzing itat a high temperature generally within the range of 600-900° C. in aninert, oxygen-depleted atmosphere using gases like argon or nitrogen,followed by an activation step in which the carbonized material isexposed to an oxidizing atmosphere provided by, e.g., carbon dioxide,oxygen, or steam at a high temperature usually within the range of600-1200° C. The carbonization step produces a large number ofmicropores within the surface of the carbonaceous starting material. Thephysical activation step is used to drive off chemical compounds whichmight clog these pores. Thus, the very high temperatures of physicalactivation are used to increase the hydrophobic adsorption capacity ofthe starting material. But these high temperatures will also tend tosoften the carbonized and activated carbon particles, and destroy thecation-exchange properties.

As for the case of chemical activation, when some of the energy requiredfor a reaction is provided by a preceding exothermic chemical reaction,there is said to be “chemical activation.” For chemical activation,pyrolysis char, carbonized product, or carbonaceous material would beimpregnated with some chemical reagents, such as phosphoric acid, zincchloride, alkaline hydroxides, and ferric chloride. Under conventionalchemical activation, the material can be then carbonized at a lowertemperature (e.g., 450-900° C.), which is still significantly highcompared against the 200-275° C. partial activation temperature range ofthis invention. This heat treatment will destroy the cation-exchangesites of the material.

As for the case of chemical modification, the carbonaceous material willbe treated with, e.g., sulfuric acid to increase its cation-exchangesites by adding SO₃ ⁻ groups to the surface structure to improve thecation-exchange capacity. But once again the chemical modificationprocess is employed to increase the cation-exchange capacity whiledecreasing the hardness of the carbonaceous material without preservingthe natural cation-exchange properties of the peat material. Bymaterially softening the peat granules or pellets, it therefore willbecome necessary to reform the granules or pellets with the assistanceof a binder additive after the activation step.

Indeed, the process of the present invention does not employ chemicalactivation, nor chemical modification. Instead, the process of thepresent invention seeks to partially activate the peat granules to anincomplete degree using relatively low temperatures for a relativelylimited time period, without addition of chemical groups via chemicalmodification in order to increase granule hardness while maintaining orat least minimizing the decrease in cation-exchange capacity of theheat-activated peat material.

Chemical Treatment Process for the Thermally-Activated Sorption Material

In an important aspect of the process of the present invention, thethermally activated peat granules 22 having desired degrees of hardnessand cation-exchange capacity characteristics are treated to a chemicaltreatment process 30 after the thermal activation step 20, as shown inFIG. 2. First, the peat granules are immersed in an acid solution like a1 molar (lesser or greater) solution of hydrochloric acid, formic acid,acetic acid, sulfuric acid, nitric acid, or phosphoric acid. Theresulting chemical reactions for this acid solution treatment step 32can be carried out at room temperature, but proceed much faster (andmore cost effectively) at elevated temperatures. Favorable results areobtained at temperatures as high as 100° C. (210° F.). At the upper endof this temperature range, reaction time can be shortened from 24 hoursto 10 minutes. The acid solution will dissolve the mineral forms ofcalcium, manganese, iron, and possibly other metals.

This acid solution treatment step seeks to remediate one of theintrinsic flaws of natural peat. Peat material has been formed by naturein a metal-enhanced environment. The ground and surface waters that feedwetland systems are generally rich in minerals and metals. Inparticular, the waters of northern Minnesota, because of the geology ofthe region, have raised concentrations of manganese. Manganese is abenign metal abundant in the glacial till that was uniformly depositedacross the upper Midwest during the last glacial events. Manganese has acomplicated chemistry and readily morphs between dissolved and mineralforms depending on the chemical matrix of the water.

As peat forms, manganese is accumulated in two ways. First, thedissolved form of the metal is adsorbed onto the active sites of theorganic surface and held there by chemical bonds. Second, dissolvedmanganese precipitates inside the peat matrix and results in theaccretion of interstitial minerals. Both types of accumulation result inincreased manganese concentrations of the natural peat.

Following the acid solution reaction step 32, the acid-treated peatgranules are rinsed with water in either a batch process or continuousprocess to remove metal ions from pore spaces and surfaces of the peatgranule until the test for the presence of calcium ions is negative.This rinse step 34 can also be conducted at room temperature, but ismore cost-effectively done at temperatures as high as 93° C. (200° F.).the manganese, calcium, and other cations, as well as residual acid fromthe peat granule surface. This rinsing step is repeated one more time,preferably six more times, or until the test for presence of calciumand/or chloride ion is negative.

Following this rinse step, metal ions (comprising mostly calcium,manganese and iron ions) need to be removed from the complexation andion exchange sites (where they are weakly held) on the internal andexternal surfaces of the peat granule. This is accomplished by immersingthe peat granule in a 1 molar (lesser or greater) solution of sodiumchloride or other salt solution of Na⁺, Li⁺, K⁺, or Cs⁺. Again, thesechemical reactions for this salt solution treatment step 36 can becarried out at room temperature, but proceed much faster (and morecost-effectively) at temperatures as high as 100° C. (210° F.). At theupper end of this temperature range, reaction time can be shortened from24 hours to 90 minutes. The salt solution will displace the metal ionsfrom the complexation and ion exchange sites in much the same way assodium or magnesium ions are used to displace metal ions in theregeneration of standard ion exchange resins.

Following this salt solution treatment step, the peat granules 36 arerinsed in water to remove the residual salt solution and any remainingmetal ions from the internal and external surfaces of the peat granule.This rinse step 38 should be continued until the concentration ofchloride ions is down to an acceptable level. Again, this can be done atroom temperature, but proceeds at a much faster rate at a temperature of100° C. (210° F.).

The finished peat granule sorbent medium 40 following the chemicaltreatment process 30 will exhibit approximately the same granulehardness as for the thermally-activated granule of step 20. Thus, thischemical treatment process does not diminish the important peat granuleharness properties achieved through thermal activation.

The final thermally-activated, chemically-treated peat product willtypically have a granular size distribution as shown below in Table 1with about 95% of the granules falling within the 16-50 mesh size range.

TABLE 1 Stays on APTsorb III batch # 05.12.11 10 mesh   0% 16 mesh 21.0%20 mesh 34.0% 30 mesh 24.7% 50 mesh 14.8% Bottom pan  5.0%

The Ball-Pan Hardness value for the thermally-activated,chemically-treated peat granules will be about 75-90%, preferably80-90%. Such granules will exhibit stability without losing theirability to adsorb metals in an aqueous environment at pH=1-8.

Sorption activity is measured in different ways for thethermally-activated, chemically-treated peat granule product. Unlike thecopper CEC method used for the thermally-activated,non-chemically-treated intermediary product 22, the capacity andactivity for the finished thermally-activated, chemically-treatedproduct 40 is measured through a 24-hour equilibrium with a 30,000 ppbcadmium solution in a 1:100 (w/v) ratio. Following the equilibrium andfiltering, the peat granule filtrate is analyzed for cadmiumconcentration, as a measure of adsorption activity generally, usingcadmium as proxy. A higher concentration translates into a granule withless CEC and activity. Granules chemically treated in the mannerdescribed under this invention will typically have equilibrium filtratesbetween 50 and 200 ppb cadmium, while increasing the active sites on thepeat granule surface and capacity of those granules for heavy metalcation affinity, while also minimizing the biological oxygen demand inthe treated waste water. These last three characteristics are producedby the acid solution reaction step 32 and salt solution reaction step36. The acid solution treatment step 32 and salt solution treatment step36 displace Ca⁺² and Mn⁺² ions that are occupying complexation and ionexchange sites on the internal and external surfaces of the peatgranules. This results in a net increase in CEC, increased in-siteactivity, and reduced leaching of organic molecules, as well as heavymetal contaminants, such as manganese, iron, etc.

Cadmium adsorption capacity represents another methodology for measuringsorption activity of the thermally-activated, chemically-treated peatgranules. If the granules are placed in an aqueous water solution havinga 50 ppb cadmium concentration, over time an equilibrium between cadmiumions moving between the granules and aqueous solution will be reached.There will be about 10-20 mEq Cd/100 g peat material at this 50 ppm Cdconcentration in the aqueous solution, preferably 15-18 mEq Cd/100 gpeat material. This measures the ability of the peat granules to adsorbcadmium at low equilibrium concentration in the solution.

Just as importantly, by reducing the presence of manganese cationsnaturally found in the peat granules, less manganese can leach into thewaste water stream during treatment with the thermally-activated,chemically-treated peat granules 40 of the present invention. Granulesprepared as described herein will leach less than 5 ppb manganese,preferably less than 1 ppb manganese, into water when acting as anion-exchange medium in a column contactor. Manganese is a contaminantwhose presence should be controlled in potable water. Hence, the sorbentmedium 40 retains much of its inherent cation-exchange capacity, obtainsan increased capacity for metals in solution, and has increased strengthand durability when exposed to water, and less leaching of organicmolecules. These characteristics make the media well-suited for wastewater remediation, and other treatments of aqueous and non-aqueoussolutions to remove contaminants and impurities.

Finally, another characteristic of the thermally-activated,chemically-treated peat granule product of the present invention is itsmaximum measured loading capacity for cadmium ions. This value is 35-50mEq/110 g at almost unlimited Cd⁺² concentration dosing, preferably40-45 mEq/100 g.

The following examples illustrate the process of the present inventionfor producing the sorbent medium 40 from partially decomposed organicmatter using low-temperature thermal activation and the acid solutionand salt solution chemical treatment steps. This sorption medium iscalled “APTsorb III.”

Example 1 Determining the Proper Activation Temperature Range for theThermally-Activated Peat Granules Base Process

Exemplary multifunctional granular media was prepared. Each granularmedium included peat. The peat selected was of a reed sedge typecommercially available from American Peat Technology, LLC of Aitkin,Minn.

For each of the Examples 1A, 1B, 1C, and 1D, the peat material was firstdried to a moisture content of about 40%. Using a granulating machine,this material was then compressed and dried again to a moisture level ofabout 6%. The resultant material was then crushed and sized to a rangeof about 10-30 mesh.

Observations with respect to activation temperatures, product yield,cation-exchange capacity, Ball-Pan Hardness number, and Iodine numberswere made as noted in each example, and in Table 2.

Example 1A

A process for the production of a multifunctional granular medium bymeans of partial activation of peat was used. The peat was partiallyactivated at 232° C. for about 30 minutes. The granular materialachieved a maximum temperature of 212° C. with an outlet steamtemperature in the reactor of 132° C., Two pounds of steam was used perpound of product produced. The yield of the product produced was 90% ofthe weight of the granular material input.

The product from Example 1A had a cation-exchange capacity of 120mEq/100 g of Cu²⁺. The Ball-Pan Hardness number was 88.6%. The surfacearea was 198 mg/g as determined by the Iodine number.

Example 1B

A process for the production of a multifunctional granular medium bymeans of partial activation of peat was used. The peat was partiallyactivated in an inert environment at 287° C. for about 30 minutes.

The granular material achieved a maximum temperature of 260° C. with anoutlet steam temperature in the reactor of 162° C. Two pounds of steamwas used per pound of product produced. The yield of the productproduced was 90% of the weight of the granular material input.

The product from Example 1B had a cation-exchange capacity of 92 mEq/100g of Cu²⁺. The Ball-Pan Hardness number was 96.9%. The surface area was123 mg/g as determined by the Iodine number.

Example 1C

A process for the production of a multifunctional granular medium bymeans of partial activation of peat was used. The peat was partiallyactivated at 343° C. for about 30 minutes. The granular materialachieved a maximum temperature of 326° C. with an outlet steamtemperature in the reactor of 182° C. Two pounds of steam was used perpound of product produced. The yield of the product produced was 80% ofthe weight of the granular material input.

The product from Example 1C had a cation-exchange capacity of 68 rEq/100 g of Cu²⁺. The Ball-Pan Hardness number was 97.3%. The surfacearea was 178 mg/g as determined by the Iodine number.

Example 1D

A process for the production of a multifunctional granular medium bymeans of partial activation of peat was used. The peat was partiallyactivated in an inert environment at 4827° C. for about 30 minutes. Thegranular material achieved a maximum temperature of 454° C. with anoutlet steam temperature in the reactor of 273° C. Two pounds of steamwas used per pound of product produced. The yield of the productproduced was 65% of the weight of the granular material input.

The product from Example 1D had a cation-exchange capacity of 13 mEq/100g of Cu²⁺. The Ball-Pan Hardness number was 76.4%. The surface area was304 mg/g as determined by the Iodine number.

TABLE 2 Activation Maximum Outlet Product Cation-Exchange Ball-PanIodine Temp Granule Temp Temp Yield Capacity Hardness Number Example (°C.) (° C.) (° C.) (wt. %) (mEq/100 g) (%) (mg/g) 1A 232 212 132 90 12088.6 198 1B 287 260 162 90 92 96.9 123 1C 343 326 182 80 68 97.3 178 1D482 454 273 65 13 76.4 304

It was observed for Examples 1A-1D that the cation-exchange capacity andBall-Pan Hardness numbers were within ranges satisfactory for use inion-exchange applications. The thermal activation step is conducted at alower temperature and time frame, compared with prior art chemicalactivation and physical activation processes known within the industry,that results in partial activation of the sites on the peat surface. Inthese particular examples, the peat material was partially activated forthirty minutes, which is very short when compared against prior artactivation processes. One will notice that the 232° C. temperaturecondition in Example 1A produced a partially activated peat product witha Ball-Pan Hardness value of 88.6% and a cation-exchange capacity of 120mEq/100 g of Cu²⁺, while the 287° C. temperature condition used inExample 1B produced a partially activated peat product with a Ball-PanHardness value of 90.0% and a cation-exchange capacity of 92 mEq/100 gof Cu²⁺. Untreated peat has a natural cation-exchange capacity of 120mEq/100 g of Cu²⁺ (page 4, lines 29-31). This shows that as theactivation temperature for the peat material is increased, the granulehardness increases, while the cation-exchange capacity decreases. But atthe 343° C. activation temperature of Example 1C, the granule hardnesscreeps up slightly to 97.3%, while the cation-exchange capacity crashesto 68 mEq/100 g of Cu²⁺. Meanwhile, the 482° C. activation temperatureof Example 1D causes the granule hardness to decrease to 76.4%, whilethe cation-exchange capacity plunges to a completely unacceptable 13mEq/100 g of Cu²⁺ and the Iodine number is significantly higher. Ahigher Iodine number generally indicates a greater adsorptive capacityfor organic chemicals. Therefore, though the ion-exchange capacity issomewhat compromised at the higher temperature of activation, a mediumsuch as that seen in Example 1D with an Iodine number of 304 mg/g isbetter suited for use as an organic adsorption medium. At the same time,this tradeoff between increased granule hardness and decreasedcation-exchange capacity also explains why the process of the presentinvention only partially activates the peat material, instead of thecomplete activation of the carbonaceous starting material that istypical practiced in the industry. By this partial activation processusing an activation temperature range of 175-287° C., preferably200-275° C., the inventors seek to increase granule hardness whilemaintaining or at least minimizing the decrease in the cation-exchangecapacity of the heat-activated peat material. The degree of granulehardness and cation-exchange capacity required for a particular end-useapplication will be obvious to a person of ordinary skill in the art whois equipped with the process parameters of this invention.

The data reveal that thermal activation at temperatures at the lower endof the range produces a granular medium with a higher product yield andhigher cation-exchange capacity than thermal activation at highertemperatures within the range. It was observed that the Ball-PanHardness number hits its peak at the level of thermal activationexpressed in Examples 1B and 1C. After that level of thermal activationis reached, the internal bonds in the peat granule begin to break down,causing an observed decrease in the hardness number. It was alsoobserved that thermal activation at points along the range produces agranular medium with a Ball-Pan Hardness number that is withinsatisfactory ranges for use as an ion-exchange material.

Example 2 Process for Producing Thermally-Activated

The APTsorb II peat granule media was prepared using peat of areed-sedge type commercially available from American Peat Technology,LLC of Aitkin, Minn., The raw peat material was first dried to amoisture content of about 40% wt. The dried, raw peat was extruded intopellets, dried again to reduce the moisture content to about 12% wt, andfinally crumbled and sieved. This process resulted in a multifunctionalgranular media called “bioAPT.”

The finished bioAPT peat granule with a size range of 10×30 mesh wasthen thermally activated to produce the APTsorb II media. The bioAPTgranules were introduced into a jacketed ribbon mixer. The mixer hadthermal fluid circulating through the jacket at a temperature of about300° C., thereby effectively heating the atmosphere inside the mixer.Additionally, the mixer ribbons were fitted with “lifters” that pickedup the media and dropped it through the heated atmosphere. Also, thedesign of the mixer and the resulting chemical reactions resulted in anoxygen-free atmosphere inside the mixer. The bioAPT material was heatedand mixed within this oxygen-free atmosphere for approximately 32minutes, at which point the chemical reactions necessary for thermalactivation were complete, and the granular media was converted into theAPTsorb II media. This media was then quickly cooled, using a waterspray, and the moisture content was adjusted to about 10% wt moisturelevel.

Four production trials of the APTsorb II peat granules were recorded andtested for quality control purposes. Observations with respect toactivation temperatures, product yield, copper cation exchange capacity,and ball-pan hardness were made as shown in Table 3.

TABLE 3 Copper Activation Activation Outlet Product Cation-ExchangeBall-Pan Temp Time Temp Yield Capacity Hardness Sample (° C.) (min) (°C.) (wt. %) (mEq/100 g) (%) Reed-Sedge Peat 132 5 BioAPT 148 85.7APTsorb II Run 1 302 32 200 83 134 96 APTsorb II Run 2 315 32 204 85 13597 APTsorb II Run 3 304 34 203 83 140 95 APTsorb II Run 4] 302 40 201 81125 97

A modified ASTM D3802-10 standard test method was used for purposes ofmeasuring Ball-Pan Hardness of the thermally-activated APTsorb II peatgranules. The moisture content of the media was measured using a MettlerToledo MJ33 moisture meter. Water was then added to 200 g media in orderto bring the moisture content to 35% wt. The media was mixed thoroughlyand kept for 15 min at room temperature. At the end of the equilibriumperiod, the media was free-flowing and not sticky, indicating that thecorrect moisture content had been reached. One hundred thirty grams ofthe moistened media was screened on a 50 mesh sieve shaker for 3minutes. A 100 g sub-sample (A in the formula) of media after screening(usual particle size are 10-50 mesh) was placed in the sieve catch pan,and 36 steel balls (15.9 mm diameter, 16.3 g each) were added. The catchpan was covered, and the sub-sample was shaken for 6 minutes toapproximate abrasion and attrition. Following this abrasion step, thesteel balls were removed, and the media was screened again on a 50 meshsieve for 5 minutes. The amount of media retained on the 50 mesh screenwas recorded in grams (B in the formula).

The Bali-Pan Hardness number was calculated using the followingequation:

H=B/A×100

where:

H=Ball-Pan Hardness number

B=weight of sample retained on hardness test sieve after the abrasionstep (g)

A=weight of sample loaded onto hardness pan prior to the abrasion step(g).

Generally, a higher Ball-Pan Hardness number generally indicates aharder granule that is more resistant to abrasion. A lower Ball-PanHardness number generally indicates that more media is abraded by thesteel balls and is less durable.

The method used to measure the cation-exchange capacity (“CEC”) of thethermally-activated APTsorb II peat granules was a modification of theusual CEC methodology, and represents a concession to the need for speedin the industrial research lab. The exchange of cations on the surfaceof the media is measured using the media as produced, without firstconverting the surface to an H⁺ form, and the indication of exchange ismeasured by the concentration of the exchanging ion before and aftercontact with the media. The exchanging ion in this case is copper,prepared as a 1000 ppm solution of copper using copper chloride,buffered to a pH of about 4.8. The buffer solution was prepared byadding 1.68 ml of glacial acetic acid and 9.51 g of sodium acetatetrihydrate to Type I deionized water and diluting to 1 L. The buffersolution was then used to make the 1000 ppm copper solution bydissolving 2.683 g of CuCl₂*2H₂O in the 1 L of buffer solution.

The media was dried on a Mettler Toledo MJ33 moisture meter at 160degrees ° C. until its weight was stable for 30 seconds. One gram of thedried media was then added to 100 ml of the 1000 ppm copper solution,and the mixture was stirred at around 300 RPM for 3 hrs at roomtemperature. The flask and stirring rod were positioned so that the rodmade contact against the wall of the flask, thereby effectivelypulverizing the media over the course of the stirring period. Themixture was filtered and the concentration of Cu²⁺ was measured bycolorimetry or by graphite furnace atomic absorption spectroscopy. Thecation exchange capacity of the media was calculated using followingformula:

CEC,mEq/100 g=(I−F)*20/63.5

where:

I===initial concentration of copper in the solution (ppm).

F=final concentration of copper in the solution (ppm).

The results shown in Table 2 demonstrate the repeatability andconsistency of the thermal activation method for producing the APTsorbII granule under this invention.

Example 3 Chemical Treatments of the Thermally-Activated APTsorb II PeatGranules to Produce the APTsorb III Peat Granule

This invention describes a process for improving the performance of thethermally-activated APTsorb II peat granule to minimize the leaching ofmanganese and organics into waste water streams treated by the resultingAPTsorb II granular peat material. The process used to produce thisAPTsorb III material is illustrated as follows:

A 2 L volume of a 1N solution of HCl was added to 1 kg of the APTsorb IImedia at room temperature. The mixture was kept at room temperature for24 hrs with periodic shaking in such a fashion so as not to destroy thegranules. The pH was maintained at a value of 2 or lower. This acidtreatment was completed when the concentration of calcium, manganese andother bivalent ions reached maximum concentrations in the solution asdetermined by the titration procedure described below. The mixture wasfiltered and washed six times with water or until the test for thepresence of chloride ions in the filtrate, as described below, wasnegative. The volume of combined acid and rinsing solutions was 11 L.

Following the acid treatment, 5 L of 1 M solution of NaCl was added tothe media, and the mixture was refluxed for 90 minutes. Following thereflux period, the mixture was filtered while it was still hot andwashed with water until the test for the presence of chloride ions inthe filtrate was negative. The volume of combined salt and rinsingsolutions was 8 L.

The solid part was dried at 105° C. for 24 hrs to yield 760 g ofthermally-activated and chemically-treated granular peat media calledAPTsorb III. Samples of the APTsorb III material were subjected to thequality control (QC) test as described below. The material balance forthe chemical treatment steps is shown in Table 4.

TABLE 4 Example of material balance for APTsorb III production, ReagentsAmount APTsorb II (11.2% H₂O) 1000 g 1N HCl 2 L Rinsing with H₂O 11 L 1MNaCl 5 L Rinsing with H₂O 8 L APTsorb III (QC = 160 ppb) product 760 gThe removal of the organics and chloride ions by the aqueous solution at180° C. accounts for the reduction of mass for the APTsorb III peatgranules.

The tests referred to above are critical for the production of theAPTsorb III peat granules. If the bivalent ion concentration in the acidsolution does not reach maximum while the solution pH remains below 2,it indicates that the mineral fraction that naturally occurs in theparent peat material is incompletely removed. The incomplete removal ofthis mineral fraction results in the leaching of manganese and calciumlater when the product is utilized as a filtration media. Also, the acidtreatment results in the exchange of metals for hydrogen ions on theactive surfaces of the peat material, thereby “cleaning” the impuritiesinherent in the parent peat material.

The following titration procedure was used to measure the concentrationof calcium, manganese, and other bivalent ions contained in the HClsolution that were removed from the APTsorb II material: An ammoniumbuffer was prepared by adding 20 g of ammonium chloride and 74 ml ofammonium hydroxide (28-30% NH₃) to a flask and diluting it to 1 literwith Type 1 deionized water. The pH of the buffer was 10.02. Tenmilliliters of the HCl acid treatment filtrate was added to anErlenmeyer flask and diluted with 50 ml of Type I deionized water. ThepH1 was adjusted to slightly acidic (pH=4-6) if necessary by theaddition of a 5% solution of NH₄OH in deionized water or 1N HCl. Anexcess of 0.1 N solution of EDTA in water was added, swirled, and keptat room temperature for 20 minutes to allow for complete complexationbetween the EDTA and bivalent ions present in the acid treatmentfiltrate. Three milliliters of a 4% solution of triethanolamine in typeI deionized water was added and swirled. Ten milliliters of the ammoniumbuffer solution was added so that the pH of the solution was 10.Immediately, 5-10 drops of an indicator solution of eriochrome black Twas added, and the mixture was titrated with a 0.1N solution of MgCl₂ indeionized water until the color changed from blue to pink\red.

The concentration of bivalent ions in the sample was calculated asfollows:

$C_{Sample} = \frac{\left( {C_{EDTA} \times V_{EDTA}} \right) - \left( {C_{{MgCl}\; 2} \times V_{{MgCl}\; 2}} \right)}{V_{Sample}}$

The following test was used to detect the presence of chloride ions inthe rinsing water: Five tenths milliliter of a 1% solution of silvernitrate was added to a 20 ml sample of rinsing water. If chlorides werepresent, a white precipitate in the form of silver chloride formedimmediately, which evidenced the need for additional rinsing.

The following cadmium equilibrium quality control test (“QC test”)method was used to measure the adsorption activity of peat granules. Onegram of dried media was added to 100 ml of a 30 ppm solution of Cd²⁺ inType I deionized water. The equilibrium was rolled at 8 rpm at roomtemperature (20±2° C.) in a leak-proof vessel for 24 h. The mixture wasfiltered using 0.45 μm polypropylene syringe filter membrane. The liquidfraction was preserved by adding concentrated HNO₃ and analyzed by GFAAspectroscopy for the concentration of Cd²⁺ and Mn²⁺ ions. This proceduremeasures the activity of the media: a lower concentration of Cd²⁺ in thesolution translates into more of the cadmium being adsorbed onto themedia and thereby indicates greater activity.

Example 4 Measurement of Naturally Occurring Heavy Metals in PeatMaterials

The concentrations of manganese and cadmium contained in raw peatsamples were determined. The samples came from the reed-sedge depositused by American Peat Technology to produce its granular products, and asample collected north of Detroit Lakes, Minn. Additionally, APTsorb IIpeat granules were analyzed as a comparison.

The samples were dried for 24 hrs at 105° C. and cooled in a desiccator.A crucible was pre-fired by heating to 550° C. for 2 h in a mufflefurnace. After the crucible was cooled, 0.250 g of dry sample added tothe crucible and the sample was carbonized at 150° C. for 30 min. Thetemperature was then increased to 550° C. and ashed for 4 h. The colorof ash was grayish-white. The residue was digested by adding 10 ml ofconcentrated HNO₃ and heating it to 95° C.±5° C. using a ribbed watchglass as a cover. The heat was monitored to result in a gentle refluxfor 10 to 15 min. The reaction mixture was cooled, and a 5 ml ofconcentrated HNO₃ was added, the cover was replaced, and the reactionmixture refluxed for 30 additional minutes. Care was taken to maintain acovering of solution over the bottom of the vessel at all times. Ifbrown fumes were generated, indicating oxidation of the sample by HNO₃,the second addition step was repeated until no brown fumes were givenoff by the sample, thereby indicating the complete reaction with HNO₃.The reaction mixture was cooled and diluted to 100 ml with deionizedwater. The solids were filtered on Whatman No. 542 filter paper, and thefiltrate was analyzed by graphite furnace atomic adsorptionspectrophotometer. The results for manganese and cadmium are shown inTable 5.

TABLE 5 Media C_(Mn) (mg/g) C_(Cd) (mg/g) Raw peat from Aitkin, MN(reed-sedge) 0.217 0.00025 APTsorb II 0.413 0.00036 Raw peat fromDetroit Lakes, MN (reed- 0.231 0.00036 sedge peat)

As can be seen in Table 4, both the raw peat samples containapproximately the same concentration of manganese, indicating peatacross Northern Minnesota was exposed to ground water laden withmanganese over the years. As expected, the APTsorb II peat granulescontain approximately twice the concentration of manganese, reflectingthe densification of the product as it is produced. At the same time,the peat granules contain less peat material than the starting raw peatmaterial due to the yields under the production process being less than100%. Thus, the same amount of manganese distributed over the smallerpeat mass in the denominator causes the concentration of manganese inthe APTsorb II granules to be higher in Table 5.

Example 5 Leaching of Manganese into Water

The presence of manganese contained in the natural peat source materialresults in the leaching of manganese from the APTsorb II granules intoaqueous solutions, including treated water streams or aqueous solutions.The bulk of this leaching stems from the mineral form of the metal whichwas precipitated inside the peat matrix as it was being formed.

Equilibrium tests were conducted for the three samples from Table 5. A10 g of media was added to 100 ml of deionized Type I water and rolledat 8 rpm for 48 hours at room temperature. The mixture was filtered andthe filtrate was preserved with nitric acid. The concentration ofmanganese in the water was analyzed by graphite furnace atomicadsorption spectrophotometer (GFAAS). The results are shown in Table 6below.

TABLE 6 Media:Water = 1:10, 48 hrs Media C_(Mn) (ppb) Raw peat fromAitkin, MN (reed-sedge peat) 450 APTsorb II granules 150 Raw peat fromDetroit Lakes, MN (reed- 445 sedge peat)

The raw peats from Aitkin, Minn. and Detroit Lakes, Minn. show similarleaching propensities, indicating similarity in geology. The mineralfraction of the manganese accumulation accounts for the bulk of theleaching, because manganese that is chemically adsorbed onto the peatsurface is not readily released by water.

The APTsorb II peat granules showed less leaching into the watersolution than the raw peat media samples, thereby reflecting a certainamount of fixing of the natural manganese during the thermal activationstep. Nonetheless, the APTsorb II granules still exhibited enoughleaching of manganese into the water solution to cause a concern,especially given that it is a filtration media for heavy metals.

Example 6 The Effect of the Treatment of Thermally-Activated PeatGranules (APTsorb II) with Acid Alone

APTsorb II media was treated with a solution of HCl in deionized water,as well as successive treatments with HCl, HNO₃, and H₂SO₄ acidsolutions. In each case, 500 g of APTsorb II material was added to 1 Lof a 1N acid solution. In the case of the three successive acidstreatment, the material was treated with the acids in series, notsimultaneously, with rinsing steps between each acid treatment.Following the acid treatments, the samples were subjected to the cadmiumequilibrium QC test, and the manganese leaching tests described above.Additionally, the manganese leaching test was modified to include anaqueous solution with a pH of 2. The filtrates were preserved withconcentrated HNO₃ and then analyzed for manganese and cadmiumconcentrations by graphite furnace atomic adsorption spectrometry. Theresults are shown in Table 7.

TABLE 7 Peat Media HCl, HNO₃, APTsorb II H₂SO₄ acid- (untreatedHCl-treated treated Solution Metal control APTsorb II APTsorb II DIwater C_(Mn), ppb 328 75 2 DI water C_(Mn), ppb 2475 1170 159 pH = 230,000 ppb C_(Mn), ppb 420 121 20 Cd²⁺ solution C_(Cd), ppb 1400 23004400

The acidified water solution caused a much higher level of manganeseleaching from all three media compared against the plain deionized watersolution. This is further supported by increasingly reduced levels ofmanganese leaching, across all solutions, as acid treatment becomes moreaggressive. The three-acid treated sample yielded extremely low levelsof manganese leaching in deionized water, thereby demonstrating theefficacy of the acid treatment step of the present invention.

Although the matter of manganese leaching is largely addressed byaggressive acid treatment, it gives rise to another limitation: theability of the media to adsorb cadmium is restricted. This cadmiumadsorption activity is decreased as acid treatments become moreaggressive. The result reported in Table 6 in the C_(Cd), ppb rowrepresents a measurement of how much cadmium was left in the aqueous30,000 ppb cadmium-laden solution after contact with the peat media. Theuntreated APTsorb II granules left 1400 ppb cadmium in solution, whilethe three-acid-treated APTsorb II granules left 4400 ppb cadmium insolution, indicating more cadmium removal activity by the untreatedAPTsorb II control media. Moreover, the cadmium equilibrium QC test ofthree-acid treated media yielded a higher level of manganeseconcentration over the DI water equilibrium, suggesting that manganeseions may remain on the active sites and can be replaced by othercompeting ions when they are present. This indication lends itself tothe need for an additional treatment step to further free the activesites in the peat granules of natural manganese—the salt treatment stepof the present invention.

Example 7 The Effect of the Treatment of Thermally-Activated PeatGranules (APTsorb II) with Salt Alone

Acid treatment of the APTsorb II peat granules has been demonstrated toremove the bulk of the natural manganese, but has deleterious effects onthe adsorption capacity of the media. This further suggests that acidtreatment alone does not clear the active sites of manganese. Becausethe active sites are exchange sites, the common practice ofregeneration—where an ion-exchange media is renewed by replacing thetoxic, sorbed ion with an innocuous ion such as sodium or magnesium—is alikely solution for displacing the manganese and reducing the leachingissue while at the same time retaining the sorption capacity.

One hundred grams of APTsorb II peat granules was added to 500 ml of a 1M solution of NaCl. One mixture was heated to 80° C. for 90 min withperiodic shaking in such a fashion so as not to destroy the granules. Asecond mixture was kept at room temperature for 24 h, and againperiodically shaken so as to not destroy the granules. Following thereaction time, the media was filtered (while it was still hot, in thecase of the 80° C. sample) and washed with water until the test for thepresence of chloride ions in the filtrate was negative. Adsorptionactivity of the samples by the cadmium equilibrium test (QC test) wasmeasured as described above. The filtrates were analyzed for manganeseand cadmium by graphite furnace atomic absorption spectrometry. Theresults are shown in Table 8 below.

TABLE 8 Effect of treatment of APTsorb II with a solution of NaCl inwater Treatment solution 1 M NaCl in H2O T (° C.) 25 80 Treatment time,hrs 24 1.5 Concentration of Cd and Mn in the NaCl solution aftertreatment C _(Cd), ppb 8 13 C _(Mn), ppb 8,000 14,100 Cd equilibriumtest using a 30,000 ppb solution (QC test). C _(Cd), ppb 750 380 C_(Mn), ppb 84 56

The concentration of cadmium remaining in solution after the cadmiumequilibrium QC test was 750 ppb at 25° C. and 380 ppb at 80° C.,indicating that the adsorption activity of the salt-treated APTsorb IIgranules increased as the treatment temperature increased from 25° C. to80° C. Additionally, the concentration of manganese in the treatmentsolution also increased from 8,000 ppb to 14,100 ppb, suggesting thatthe salt treatment is more effective when heated. However, the cadmiumequilibrium QC test revealed that manganese is still leaching from themedia, reaching the concentration of 84 ppb and 56 ppb after treatmentat 25° C. and 80° C., respectively. The presence of manganese in thesolution after the QC test indicates that not all manganese ions wereremoved during the salt treatment and suggests that the treatment ofAPTsorb II granules with salt solution is not enough to remove the bulkof the natural manganese and, consequently, make the active sitesavailable for adsorption. This result suggests that a combination ofacid and salt treatment, in series, may be necessary to achieve thegoal.

Example 8 The Effect of the Treatment of Thermally-Activated PeatGranules (APTsorb II) With Acid Solution Followed By Salt Solution

The supporting data from Examples 6 and 7 suggested a the benefits of atwo-part chemical treatment process for producing APTsorb III peatgranules. The results suggest that the use of a single acid followed bya salt treatment with heat may reduce the leaching of manganese whileretaining the activity and capacity for adsorption and lead to theprocess for production of the APTsorb III material.

The APTsorb III peat granules were produced by mixing 500 g of APTsorbII material and 1 L of 1 N HCl. The mixture was kept at room temperaturefor 24 h with periodic shaking as to not destroy the granules. After theacid treatment, the media was rinsed with deionized water until thefiltrate was free of chlorides as described in the test above. The mediawas then mixed with 5 L of 1 M NaCl solution and heated. The mixture washeld at 90-100° C. for 90 minutes, filtered while still hot, and rinseduntil free of chlorides as described above. The treated media was thendried for 24 h at 105° C.

The adsorption activity of the APTsorb III material was measured by thecadmium equilibrium QC test. Filtrates were preserved and analyzed formanganese and cadmium, using graphite furnace atomic absorptionspectrometry. The results are shown in Table 9 below.

TABLE 9 Concentration of Mn and Cd after QC test with initialconcentration of Cd equal 30,000 ppb. Raw reed- APTsorb III APTsorb IIIsedge peat APTsorb II 1 kg scale 500 lb scale C _(Cd), ppb 1200 1400 16050 C _(Mn), ppb 200 420 0.9 1

As can be seen, the acid and salt treatments together essentiallyeliminated the leaching of manganese. At the same time, the cadmiumadsorption of acid/salt-treated media indicates much higher activitycompared with the parent peat material and the APTsorb II material.

The first step, an acid treatment step, effectively removed the greaterpart of the mineral form of manganese and other contaminants, and likelyalso displaced some of the ions that are filling ion-exchange sites withhydrogen. The second step, a salt treatment step, regenerated the otheractive sites besides ion-exchange on the media to a sodium form. Sodium,which is a single-valet cation, is not the preferred ion for thosesites, but the equilibrium of the process is driven by concentration andheat to the sodium-form state. Therefore, when the media is subjected toa target metal, competing ions with a valence of +2 readily displace thesodium ions, which makes the media more active towards sorption ofmetals compared with the parent material.

The result of this mechanism is illustrated in Table 8, where theconcentration of manganese leaching into the solution is reduced from420 ppb for the APTsorb II material to 1 ppb for the APTsorb IIIproduct. Simultaneously, the activity of the APTsorb III product isenhanced over the APTsorb II material, and even the parent peatmaterial. The APTsorb III product left between 50 and 160 ppb cadmium insolution, versus 1200 and 1400 ppb for raw peat and the APTsorb IImaterial, respectively. Thus, the APTsorb III product of the presentinvention amply demonstrates the value of both the acid solutiontreatment and the salt solution treatment in series.

Example 9 Activity of APTsorb III Peat Granules for Adsorption of HeavyMetals

The equilibrium test was performed using APTsorb II material and theAPTsorb III product with other metal ions in order to determine theirrespective affinities for heavy metals other than cadmium, and tocompare the performance gains of the APTsorb III product over theAPTsorb II material. The typical test procedure uses 1 g of APTsorb peatgranules dried at 105° C. for 24 hrs, which was added to 100 ml of asolution of metal ion in Type I deionized water. The mixture was tumbledin an end-over-end fashion at 8-28 rpm at room temperature (20±2° C.) ina leak-proof vessel for 24 hrs. The mixture was filtered using 0.45 μmpolypropylene filter membrane, and the filtrate was preserved by addingof a solution of HNO₃. The initial and final concentrations of metalions were measured by graphite furnace atomic adsorptionspectrophotometry. The results are shown in Table 10 and FIG. 3.

TABLE 10 Comparison of adsorption activity of APTsorb II and APTsorb IIIgranular peat products. Metal ions Co²⁺ Cu²⁺ Ni²⁺ Zn²⁺ Cd²⁺ Pb²⁺C_(initial), ppb 29000 22000 23000 32000 30000 51,000 APTsorb II peatgranules C_(final), ppb 2100 1300 1900 1400 960 980 Percent of removal(%) 87.65 87.65 92.78 82.73 92.22 96.16 APTsorb III peat granulesC_(final), ppb 360 500 420 300 50 380 Percent of removal (%) 98.76 97.7398.17 99.06 99.83 99.25In all cases, the adsorption activity of the APTsorb III peat productwas dramatically improved after chemical treatments of the APTsorb IImaterial. These results demonstrate that the chemical treatment of peatmedia of the present invention increases the activity of the surfacechemistry of the peat granules, resulting in a more active adsorptionmedia for heavy metal adsorption.

Example 10 The Activity of the APTsorb II Product Toward Adsorption ofMn and Cd Using a Column

The kinetic performance of the APTsorb III peat product was determinedby bench-scale columns using varying flow rates (flow velocity). TheAPTsorb III peat granules were pre-wetted in Type I deionized water fora minimum of 3 hours. The column was loaded from the top, first with aplastic screen to retain the media inside the column, then a layer ofHCl-washed Red Flint filter gravel (granular size 3-5 mm), and then withpre-wetted APTsorb III. A second plastic screen was placed on top of theAPTsorb III granules, and finally a second layer of filter gravel wasspread on the top of the screen. The influent flow was controlled by aperistaltic pump, and all flows were bottom feed to produce an upwardflow. A minimum of 10 bed volumes of Type I deionized water were pumpedthrough the column prior to the testing solution. A solution of 30 mg/Lcadmium or manganese in water was then introduced into the column. Thesolutions were at room temperature, and the pH was not adjusted,Effluent samples were periodically collected, preserved with HNO₃, andanalyzed by graphite furnace atomic absorption spectroscopy. The resultsare reported as shown in FIGS. 4 and 5 and Table 11.

TABLE 11 Column adsorption data for Mn and Cd. Flow Column Bed AspectFlow Flow Breakthrough C_(influent), rate, m_(granules), diameter,depth, ratio of bed, rate, velocity, capacity at 50 ppb ppm ml/min g cmcm (Height:Width) BV/hr m/hr mg/g mmol/100 g Adsorption of Cd²⁺ 30 572.3 6.2 5 0.81 1.99 0.10 10.15 8.90 29 20 72.3 6.2 5 0.81 7.95 0.405.75 5.05 Adsorption of Mn²⁺ 30 1 20 1.5 21.5 14.33 0.57 0.34 2.39 4.6430 3 20 1.5 21.5 14.33 1.70 1.02 1.77 3.21 30 5 20 1.5 21.5 14.33 2.831.70 1.54 2.80

The sorption capacity of the APTsorb III peat granule product isdependent upon a flow velocity of influent. As can be seen from theresults of Table 10, the capacity of the peat granule for holdingcadmium is twice the value (8.90 mmol/100 g) at 0.10 ml/hr than what itis (5.05 mmol/100 g) at the higher 0.40 m/hr flow velocity. The capacityof the APTsorb III granule is less for manganese, because the peatmaterial has a smaller affinity for Mn⁺² cations than Cd⁺² cations. Timeis a critical component for metal cations to chemically attachthemselves to the active sites on the surface of the peat granule. Thus,smaller flow velocities for the column may be beneficial.

Example 11

A Ba(OAc)₂, cation-exchange test may be performed as follows:

A 2.00 g sample of air-dried sorbent was placed in a 300-mL flask,100-mL of 0.5 N hydrochloric acid (HCl, analytical grade), was added andthe flask was shaken in a mechanical shaker for 2 hours. The reactionmixture was filtrated through filter paper and the solid was washed with100-mL measures of distilled-deionized water until a 10-mL sample of thewash showed no precipitate with 3 mL of 1% silver nitrate (AgNO3). Themoist sorbent was then transferred to a clean 300-mL flask and shaken ina mechanical shaker for 1 hour with 100 mL, of 0.5 N barium acetate(Ba(OAc)2) solution. The solution was then filtered and washed withthree 100-mL portions of deionized water. The sorbent was then discardedand the washings were titrated with 0.5 N sodium hydroxide, using 5drops of phenopthaline as an indicator. The CEC was calculated asfollows: meq/100 g air-dried sorbent=(V NaOH mL×normalityNaOH×100)/weight of sorbent (g).

In aqueous solutions containing high concentrations of cadmium, thethermally-activated and chemically-treated sorption medium discussedabove will treat the aqueous solution in accordance with Reaction Ishown below:

The metal cations M⁺ located on the peat granule active sites, which aredescribed above as being Na⁺ resulting from the sodium chloride saltsolution used to chemically treat the sorption medium, will be displacedby the cadmium (Cd²⁺) cations found in the aqueous solution during theion exchange treatment process with the result that the cadmium cationsare adsorbed by the peat granules with the benign Na⁺ cations dispersedin the treated aqueous solution. The adsorption capacity of the sodiumcation-loaded peat granule sorption medium for the cadmium contaminantsin the aqueous solution is described in Example 12 below:

Example 12 Determining the Adsorption Capacity for Cadmium by the SodiumCation-Loaded Sorption Medium General Experimental Column Procedure

The experimental set-up for the column system consisted of a plasticcolumn resulting in a bed size of 62 mm in diameter and 50 mm deep asshown. 72.3 g of APTsorb III sorption medium loaded with sodium cationson its active sites prepared in accordance with Example 3, and having aparticle size distribution of between 10-50 mesh, was submerged in typeI deionized water (18.2 MOhm) for 10 hrs, to wet the surface of thegranules and allow the granules to swell. Plastic mesh was installed atboth the top and the bottom of the column. The column was packed with 20mm of HCl-washed Red Flint filter gravel (granular size 3-5 mm)¹ andthen with 50 mm of pre-wetted APTsorb III. Five bed volumes of type Ideionized water were pumped through the column prior to the testingsolution. A solution of 30 mg/L cadmium in water was then pumped from aholding tank to the bottom of the column (up-flow, fixed-bed). Theliquid flow rate was controlled by a peristaltic pump. All experimentswere performed at 25° C. and at an initial pH of 5.7. In order to ensurethe formation of a complete breakthrough curve, water samples werecollected using a Foxy 200 fraction collector. In the event that airstarted to accumulate in the column, the air was either forced out bytapping the column walls or the top of the column was removed. ¹ RedFlint Rock and Stone, 717 Short Street, Eau Claire, Wis. 54701, phone:800.238.9139,

Each water sample was preserved by addition of a solution of HNO₃(TraceMetal Grade) in water and analyzed for the concentration of Cd²⁺using a graphite furnace atomic absorption spectroscopy technique andZn²⁺ using flame ionization atomic absorption spectroscopy technique.Breakthrough behavior was evaluated by plotting the cadmium and zincsolution concentrations in the effluent as a function of the totalnumber of bed volumes that had been treated. The amount of metal ionadsorbed in the column was determined from the area above thebreakthrough curve assuming the breakthrough happens when theconcentration of the metal in the effluent reaches 50 ppb. Theabsorption capacity of modified APTsorb III granules was verified bydigesting the spent granules and measuring the concentration of themetal ions.

Specific Column Procedure for Cadmium Adsorption Determination

Using the General Column Procedure described above, a synthetic solutionof cadmium with concentration 6 ppm was prepared by dissolving cadmiumchloride in Type I deionized water (18.2 MOhm). Na-APTsorb II peatgranules were loaded into the column having a column diameter of 6.2 cm,a bed depth of 5 cm, and a bed volume of 150.95 cm³. Employing a flowrate for the cadmium aqueous solution of 1.99 BV/hr and a contact timeof 30.19 minutes, the breakthrough capacity for adsorption of cadmium atbreakthrough concentration 50 ppb was found to be 16.43 mg/g at 0.1 m/hrflow velocity. “Breakthrough capacity” measures the effective totalloading of the peat adsorption sites with cadmium. At this point intime, the cadmium coming off those sites and dispersed back into theaqueous stream is so high that the 50 ppb Cd²⁺ threshold is reached andthe sorption medium is spent. The data for this experiment is shown inTable 12 and FIG. 6.

TABLE 12 Flow Bed Flow Flow Contact Breakthrough Cd feed rate, ColumnBed depth, volume, rate, velocity, time, Number of capacity at 50Granules grade, ppm ml/min m_(granules), g diameter, cm cm cm³ BV/hrm/hr min treated BV ppb, mg/g Na-APTsorb III 6 5 72 6.2 5 150.95 1.990.10 30.19 1306 16.43With waste waters containing high concentrations of cadmium, there is acoefficient that will define this equilibrium adsorption by the peatgranules for Cd²⁺. This ultimately controls the 16.43 mg/g breakthroughcapacity value.

But, if the aqueous solution contains a second metal cation like zinc(Zn²⁺), which frequently occurs in waste waters, then the presence ofthe Zn²⁺ cations will retard the adsorption capacity of the peat granulesorption medium for the Cd²⁺ cations. Because the Zn²⁺ cations usuallyappear in the waste water solution at higher concentrations than theCd²⁺ cations, the Zn²⁺ cations occupy many of the active sites on thepeat granules to the exclusion of Cd²⁺ adsorption. This problem isdemonstrated in Experiment 13 below:

Experiment 13 Determining the Adsorption Capacity for Cadmium in thePresence of Zinc B the Sodium Cation-Loaded Sorption Medium

Using the General Column Procedure described above, a synthetic solutionof cadmium and zinc with concentrations 6 ppm cadmium and 30 ppm zincwas prepared by dissolving cadmium chloride and zinc sulfate in Type Ideionized water (18.2 MOhm). Na-APTsorb III peat granules were loadedinto the column having a column diameter of 6.2 cm, a bed depth of 10cm, and a bed volume of 301.91 cm³. Employing a flow rate for thecadmium/zinc aqueous solution of 3.97 BV/hr, the breakthrough capacityfor adsorption of cadmium at breakthrough concentration 50 ppb was foundto be only 0.89 mg/g at 0.4 m/hr flow velocity. The data for thisexperiment is shown in Table 13 and FIG. 7. This demonstrates theunwanted competition by the zinc cations for the active sites on thesodium-loaded peat granules to the exclusion of cadmium adsorptionduring the treatment process, which resulted in the breakthroughcapacity for the sodium-loaded peat granule sorption medium falling from16.43 mg/g to 0.89 mg/g. This represents a problem for treatment ofaqueous solutions using the sodium-loaded peat granule sorption mediumto remove the Cd²⁺ cations where Zn²⁺ cations are present.

TABLE 13 Bed Bed  

  Zn feed Cd feed Flow rate, m_(granules), Column depth, volume, Flowrate, Flow Capacity capacity at 50 grade, ppm grade, ppm ml/min gdiameter, cm cm cm³ BV/h velocity, m/h Zn, mg/g ppb, mg/g 29.3 5.8 20148 6.2 10.00 301.91 3.97 0.40 4.49 0.89 33 5.3 1 63.11 2.54 21.59109.40 0.55 0.12 7.01 1.13

indicates data missing or illegible when filed

In a second experiment, a different column having a 2.54 cm diameter,21.59 bed depth, and 109.40 bed volume was employed with the sameNa-APTsorb sorption medium. While the aqueous cadmium/zinc solution wassubstantially similar to the concentrations of the Cd²⁺ and Zn²⁺ cationsfound in the aqueous solution used in the first experiment describedabove, the flow velocity was slowed down to 0.12 min/r, resulting ingreater contact time by the aqueous solution with the peat granules.Even so, the breakthrough capacity for Cd²⁺ at 50 ppb was measured asonly 1.13 mg/g, which is still substantially lower than the 16.43 mg/gbreakthrough value for the cadmium-only aqueous solution used inExperiment 12.

In order to solve this problem of substantially decreased adsorptioncapacity of the sorption medium for Cd²⁺ cations, Zn²⁺ cations insteadof Na⁺ cations can be placed on the active sites of the peat materialduring the salt solution treatment step 36 described above. Thus, azinc-based compound like ZnCl₂ or ZnSO₄ should be substituted for theNaCl previously described for this salt solution treatment step. Thepresence of these Zn²⁺ cations on the active sites of the peat granuleswill alter the coefficient that defines the equilibrium and influencesthe adsorption capacity more in favor of Cd²⁺ adsorption by the sorptionmedium at the expense of Zn²⁺ adsorption. This will allow the end userto target Cd²⁺ adsorption to leave more of the Zn⁺ cations in theaqueous solution during the treatment process by means of selecting asorption medium for which a special preselected solution of solublesalts was used that favors Reaction I over Reaction II.

For purposes of this invention, this special preselected solution ofsoluble salts comprises any compound having a cation constituent and ananion constituent where:

-   -   the cation constitutent is selected from the group consisting of        any 1⁺ or 2⁺ cation of, e.g., ammonium (NH₄ ⁺), ammonium groups        (NR₄ ⁺), potassium, lithium, cesium, beryllium, magnesium,        calcium, barium, manganese, copper, zinc, strontium, iron, or        lead; and    -   the anion constituent is selected from the group consisting of        SO₄ ²⁻, SO₃ ²⁻, NO₃ ⁻, NO₂ ⁻, PO₄ ²⁻, Cl⁻, I⁻, Br⁻, F⁻, HCOO⁻,        CH₃COO⁻, C₂H₅COO⁻, C₃H₇COO⁻, C₄H₉COO⁻, ClO₄ ⁻, HCO₃ ⁻, or CO₃        ²⁻.        Because these particular cations represent less toxic metals,        their placement on the active sites of the sorption medium via        the salt solution treatment step 36 to enable the sorption        medium to adsorb a major toxic metal like cadmium, while leaving        most of the less toxic metals in the aqueous solution during the        treatment process will produce a much greater adsorption        capacity of the sorption medium for the major toxic metal, as        measured by the breakthrough capacity. This modified salt        solution treatment step for the sorption medium using the        preselected solution of soluble salts should result in an        improved breakthrough capacity for cadmium up to 16.43 mg/g at        50 ppb of the major toxic metal.

This modified process for preparing the sorption medium using thepreselected solution of soluble salts compound is demonstrated inExample 14 below:

Example 14 Preparation of Modified Sorption Medium Using a PreselectedMetal Cation Salt Compound

The process used to produce a Zn form of the APTsorb II material isillustrated as follows:

A 2 L volume of a 1N solution of HCl was added to 1 kg of the APTsorb IImedia at room temperature. The mixture was kept at room temperature for24 hrs with periodic shaking in such a fashion so as not to destroy thegranules. The pH was maintained at a value of 2 or lower. This acidtreatment was completed when the concentration of calcium, manganese andother bivalent ions reached maximum concentrations in the solution asdetermined by the titration procedure described below. The mixture wasfiltered and washed six times with water or until the test for thepresence of chloride ions in the filtrate, as described below, wasnegative. The volume of combined acid and rinsing solutions was 11 L.

Following the acid treatment, 5 L of 1M solution of ZnSO₄ was added tothe media, and the mixture was heated at 80-100° C. for 90 minutes.Following the heating period, the mixture was filtered while it wasstill hot and washed with water until the test for the presence ofchloride and sulfate ions in the filtrate was negative.

The solid part was dried at 105° C. for 24 hrs to yield 760 g ofthermally-activated and chemically-treated granular peat media calledAPTsorb III-Zn.

The above specification, drawings, examples, and data provide a completedescription of the thermally-activated, chemically-treated sorptionmedia and associated preparation method of the present invention. Sincemany embodiments of the invention can be made without departing from thespirit and scope of the invention, the invention resides in the claimshereinafter appended.

We claim:
 1. A process for the production from partially decomposedorganic matter of a sorption media for use in the treatment of aqueoussolutions to remove at least one type of aqueous contaminant, comprisingthe steps of: (a) supplying an amount of the partially decomposedmoisture-bearing organic matter to a granulating machine; (b)granulating the partially decomposed organic matter; (c) drying thegranules; (d) thermally activating the granules without chemicalactivation using an activation heat medium at a temperature of about175-287° C., wherein the granule has a Ball-Pan Hardness number of about75%-100% and is suitable for sorption of the aqueous contaminant foundin the aqueous solution; and (e) chemically treating thethermally-activated granule, comprising: (i) treatment of the granulewith an acid solution to dissolve out the mineral form of at least onetype of media contaminant naturally found in the partially decomposedorganic matter starting material to place the mineral form of the mediacontaminant into the acid solution and onto the active sorption sites inthe granule; (ii) treatment of the granule with a salt solution todisplace the mineral form of the media contaminant off the activesorption sites in the granule and into the salt solution and internalvoids in the granule; (f) wherein the thermally-activated andchemically-treated granules can sorb the aqueous contaminant from theaqueous solution without introducing the media contaminant into thetreated aqueous solution.
 2. The process of claim 1, wherein thepartially decomposed organic matter is selected from the groupconsisting of compost media, livestock manure, sewage sludge, andcombinations thereof.
 3. The process of claim 2, wherein the partiallydecomposed organic matter is compost media.
 4. The process of claim 3,wherein the compost media is selected from the group consisting of leafcompost media, peat, plant by-products, and combinations thereof.
 5. Theprocess of claim 1, wherein the aqueous solution comprises a water-basedsolution containing an environmental impurity as a solute produced bymanufacturing, agricultural, or mining industries, or populationcommunities.
 6. The process of claim 1, wherein the aqueous contaminantcomprises a chemical element or compound found in an aqueous solutionthat poses a health risk to humans or animals, or is subject toenvironmental laws or regulations.
 7. The process of claim 6, whereinthe aqueous contaminant comprises heavy metals like arsenic, lead,mercury, cadmium, manganese, iron, zinc, nickel, copper, molybdenum,cobalt, nickel, chromium, palladium, stannum, or aluminum; radioactivematerials like cesium or various isotopes of uranium; sulfates,phosphorous, selenium, boron, ammonia, refrigerants, and radon gases. 8.The process of claim 1 further comprising screening the partiallydecomposed organic matter to remove unwanted particles beforegranulating.
 9. The process of claim 8 further comprising admixingadditives with the partially decomposed organic matter after screening.10. The process of claim 9, wherein the additives are selected from thegroup consisting of binders, pH adjusters, and combinations thereof. 11.The process of claim 1, wherein the granule temperature during thedrying step is conducted at a temperature of about 80-400° C.
 12. Theprocess of claim 11, wherein the moisture level of peat granules isreduced within the drying step from about 40% wt. to about 10-14% wt.13. The process of claim 1, wherein the granules are thermally activatedin an inert environment.
 14. The process of claim 1 wherein theactivation heat medium comprises steam or carbon dioxide, nitrogen orother inert media, or combinations thereof at a temperature of about175-287° C. until the desired level of hardness and activation isachieved.
 15. The process of claim 1, wherein the thermal activationstep for the granule is carried out at a temperature of about 200-275°C.
 16. The process of claim 1, wherein the granule has a Ball-PanHardness of about 80-98%.
 17. The process of claim 1, wherein the acidsolution comprises a solution of hydrochloric acid, formic acid, aceticacid, sulfuric acid, nitric acid, or phosphoric acid.
 18. The process ofclaim 1, wherein the salt solution comprises a solution of Na⁺, Li⁺, K⁺,or Cs⁺.
 19. The process of claim 1 further comprising rinsing of thechemically-treated granule with water or other suitable substance afterthe salt solution treatment step to remove the residual salt solution orany remaining mineral form of the media contaminant from the internalvoid in the granule.
 20. The process of claim 1 further comprisingrinsing the chemically-treated granule with water or other suitablesubstance after the acid solution treatment step to remove the mediacontaminant from the active sorption sites on the granule.
 21. Theprocess of claim 1, wherein the sorption media comprises acation-exchange media, an adsorption media, or an absorption media. 22.A process for the production of a chemically-treated sorption media madefrom partially decomposed organic matter for use in the treatment ofaqueous solutions to remove at least one type of aqueous contaminant,comprising the steps of: (a) supplying an amount of a thermallyactivated, granulated, partially decomposed moisture-bearing organicmatter that was not chemically activated; (b) chemically treating thethermally-activated granule, comprising: (i) treatment of the granulewith an acid solution to dissolve out the mineral form of at least onetype of media contaminant naturally found in the partially decomposedorganic matter starting material to place the mineral form of the mediacontaminant into the acid solution and onto the active sorption sites inthe granule; (ii) treatment of the granule with a salt solution todisplace the mineral form of the media contaminant off the activesorption sites in the granule and into the salt solution and internalvoids in the granule; (c) wherein the thermally-activated andchemically-treated granules can sorb the aqueous contaminant from theaqueous solution without introducing the media contaminant into thetreated aqueous solution.
 23. The process of claim 22, wherein thethermally-activated granule has a Ball-Pan Hardness number of about75%-100%.
 24. The process of claim 23, wherein the thermally-activatedgranule has a Ball-Pan Hardness of about 80-98%.
 25. The process ofclaim 22, wherein the acid solution comprises a solution of hydrochloricacid, formic acid, acetic acid, sulfuric acid, nitric acid, orphosphoric acid.
 26. The process of claim 22, wherein the salt solutioncomprises a solution of Na⁺, Li⁺, K⁺, or Cs⁺.
 27. The process of claim22 further comprising rinsing of the chemically-treated granule withwater or other suitable substance after the salt solution treatment stepto remove the residual salt solution or any remaining mineral form ofthe media contaminant from the internal void in the granule.
 28. Theprocess of claim 22 further comprising rinsing the chemically-treatedgranule with water or other suitable substance after the acid solutiontreatment step to remove the media contaminant from the active sorptionsites on the granule.
 29. The process of claim 22, wherein the sorptionmedia comprises a cation-exchange media, an adsorption media, or anabsorption media.
 30. The process of claim 22, wherein the partiallydecomposed organic matter for the thermally-activated granule isselected from the group consisting of compost media, livestock manure,sewage sludge, and combinations thereof.
 31. The process of claim 30,wherein the partially decomposed organic matter is compost media. 32.The process of claim 31, wherein the compost media is selected from thegroup consisting of leaf compost media, peat, plant by-products, andcombinations thereof.
 33. The process of claim 22, wherein the aqueoussolution comprises a water-based solution containing an environmentalimpurity as a solute produced by manufacturing, agricultural, or miningindustries, or population communities.
 34. The process of claim 22,wherein the aqueous contaminant comprises a chemical element or compoundfound in an aqueous solution that poses a health risk to humans oranimals, or is subject to environmental laws or regulations.
 35. Theprocess of claim 34, wherein the aqueous contaminant comprises heavymetals like arsenic, lead, mercury, cadmium, manganese, iron, zinc,nickel, copper, molybdenum, cobalt, nickel, chromium, palladium,stannum, or aluminum; radioactive materials like cesium or variousisotopes of uranium; sulfates, phosphorous, selenium, boron, ammonia,refrigerants, and radon gases.
 36. A sorption medium for use in thetreatment of aqueous solutions to remove an aqueous contaminant,comprising thermally-activated, chemically-treated granules of partiallydecomposed organic matter having a Ball-Pan Hardness number of about75-90%.
 37. The sorption medium of claim 36, wherein 95% of the granuleshave a size distribution of about 16-50 mesh.
 38. The sorption medium ofclaim 36, wherein when the granules are used to treat an aqueoussolution having a 30,000 ppb cadmium concentration, the residual levelof cadmium ions remaining in the aqueous solution is about 50-200 ppb.39. The sorption medium of claim 36, wherein when the granules are usedto treat an aqueous solution having a cadmium concentration over timeafter reaching equilibrium at 50,000 ppb of cadmium in the solution, theloading capacity for cadmium ions adsorbed by the granules is about10-20 mEq/100 g.
 40. The sorption medium of claim 36, wherein when thegranules are used to treat an aqueous solution having an almostunlimited cadmium dosing concentration, the maximum measured loadingcapacity for cadmium ions on the granules is about 35-50 mEq/100 g. 41.The sorption medium of claim 36, wherein when the granules are used totreat an aqueous solution having a 30,000 ppb cadmium concentration, theamount of manganese ions leaching from the granules into the aqueoussolution does not exceed about 5 ppb.
 42. The sorption medium of claim36 further comprising admixing additives with the partially decomposedorganic matter after screening.
 43. The sorption medium of claim 42,wherein the additives are selected from the group consisting of binders,pH adjusters, and combinations thereof.
 44. The sorption medium of claim36, wherein the partially decomposed organic matter is selected from thegroup consisting of compost media, livestock manure, sewage sludge, andcombinations thereof.
 45. The sorption medium of claim 44, wherein thecompost media is selected from the group consisting of leaf compostmedia, peat, plant by-products, and combinations thereof.
 46. Thesorption medium of claim 45, wherein the compost media is leaf compostmedia.
 47. The sorption medium of claim 45, wherein the compost media ispeat.